.y  -y^-    ,-  ,, 


^S^5l 


>;±— "''«^- 


r 


^JK: 


u>4; 


"■-Sr  ^  •<■■■"<  ■  ■■■ 
.*'>^;t.-«'.\''""" 


lD 


n^JH^UKIIftf — 


Agric.  Depi   ^^.,^  ^,,1, 


hDcj- 


s 

•<^<>> 


MANUAL  OF  AGRICULTUEE 

FOR   SECONDARY   SCHOOLS 


STUDIES    IN    SOILS    AND 
CROP    PRODUCTION 


BY 


D.    O.    BARTO,   B.S. 

INSTRUCTOR    IN    SECONDARY    SCHOOL   AGRICULTURE 
COLLEGE    OF   AGRICULTURE,    UNIVERSITY 
OF    ILLINOIS 


WITH  INTRODUCTION   BY 


E.  DAVENPORT,  M.Agr.,  LL.D. 

DEAN    OF    THE    COLLEGE    OF    AGRICULTURE 
UNIVERSITY    OF   ILLINOIS 


)    i  i  i    >     > 


BOSTON,   U.SA. 
D.   C.   HEATH    &   CO.,  PUBLISHERS 

1910 


S¥? 


Copyright,  1910, 
By  D.  C.   Heath  &  Co. 


INTRODUCTION 

We  are  making  educational  history  these  days  at  a  rapid  rate, 
and  not  the  least  important  chapter  is  on  the  new  status  of  affairs 
industrial.  At  last  agriculture  is  coming  into  its  own,  and  it  will 
not  be  many  years  until  this  subject  will  have  taken  its  place  in 
the  American  secondary  school  system  as  it  is  now  taking  its  place 
within  the  colleges  and  universities. 

This  is  not  only  because  agriculture  employs  the  time  and 
absorbs  the  lives  of  a  third  of  our  people  and  feeds  us  all ;  it  is 
not  only  because  the  future  and  the  development  of  every  people 
is  limited  by  the  production  of  the  soil  it  occupies ;  it  is  not  only 
because  it  is  expedient  from  the  community  standpoint  that  this 
subject  should  be  studied  by  young  people  and  developed  by  sci- 
ence ;  it  is  largely  because,  after  all,  the  subject-matter  of  agricul- 
ture, its  method  and  its  outlook,  are  exceptionally  valuable  in 
their  influence  upon  the  individual,  educationally. 

Elsewhere  ^  I  have  written,  "  It  is  dangerous  to  attempt  to  edu- 
cate a  live  boy  with  no  reference  to  the  vocational,"  and  I  might 
add  that  it  is  dangerous  to  the  community,  as  it  is  unprofitable 
to  the  individuals,  to  fill  our  schoolhouses  day  after  day  with  young 
men  and  women  to  study  seriously  all  the  problems  of  life  except 
the  one  supreme  problem  of  how  to  make  a  living,  a  large  and  sig- 
nificant portion  of  which  problem  from  the  racial  standpoint  is  com- 
prised within  the  range  of  farming  and  farm  life. 

The  introduction  of  agriculture  into  the  secondary  schools  has 
been  delayed  from  the  same  causes  which  have  retarded  the  devel- 

1 "  Education  for  ElBciency,"  Chapter  I,  Heath  &  Co.,  1909. 

ill 

267522 


iv  INTRODUCTION 

opment  of  the  agricultural  colleges ;  viz.,  want  of  teachers,  igno- 
rance of  suitable  matter  and  methods,  and  the  lack  of  an  adequate 
literature  both  for  reference  and  for  text. 

It  has  taken  the  colleges  more  than  forty  years  to  overcome, 
even  measurably,  this  inherent  handicap  upon  a  new  academic 
subject,  rendered  more  serious  in  this  case  because  of  peculiar 
ancient  traditions  regarding  the  ideals  and  the  scope  of  education. 
In  the  last  five  years,  however,  the  future  of  these  colleges  has  not 
only  become  assured,  but  their  success  has  engendered  the  demand 
that  agriculture  be  also  taught  in  schools  other  than  colleges,  not 
only  to  relieve  congestion  there,  but  more  especially  to  bring  to 
the  masses  of  people  where  it  will  do  the  utmost  possible  good 
the  recent  findings  of  science  regarding  the  maintenance  of  the 
food  supply  of  a  people,  on  the  one  hand,  and  that  standard  of 
life  and  living  that  find  their  highest  exemplification  in  a  properly 
developed  country  life. 

The  next  place  for  agriculture,  therefore,  is  in  the  secondary 
schools,  and  their  period  of  trial  ought  to  be  far  more  brief  than 
that  of  the  colleges.  This  is  because,  though  teachers  are  yet 
to  be  produced,  the  colleges,  in  their  experience,  have  learned 
much,  both  of  matter  and  of  method,  that  can  be  transferred 
directly  into  the  secondary  school,  particularly  the  well-organized 
high  school  with  a  country  constituency.  These  same  colleges, 
too,  in  cooperation  with  the  normal  schools,  are  able  to  produce, 
and  are  already  producing,  eminently  qualified  teachers. 

From  now  on  the  supply  of  teachers  will  come  along  in  natural 
response  to  a  demand  that  takes  all  promising  candidates  at 
maximum  salaries,  so  that  the  great  business  of  the  immediate 
future,  and  one  that  must  largely  be  left  to  the  enterprise  of  indi- 
viduals and  the  initiative  of  far-seeing  publishers,  is  the  production 
of  suitable  reference  and  text-books,  for  no  subject  is  teachable 
till  it  has  an  adequate  literature. 


INTRODUCTION  V 

These  books  are  now  springing  up,  as  if  by  magic,  from  all 
sorts  of  unexpected  places.  The  surprising  fact  is  that  there  are 
so  many,  and  the  still  more  surprising  fact  is  that  they  are  so 
good  —  better  by  far,  most  of  them,  than  the  best  that  were  avail- 
able for  college  purposes  when  the  writer  was  a  student. 

Too  many  of  these  books,  unfortunately,  are  confessedly  "ele- 
mentary," whereas  it  is  not  elementary  agriculture  that  the  farmer 
most  needs.  What  he  wants  is  instruction  in  the  elementals  of 
agriculture.  It  is  the  fundamentals  of  the  subject  that  need  to 
be  emphasized  and  taught,  and  fortunately  many  of  these  books 
belie  their  titles  and  are  not,  after  all,  "elementary,"  but  elemental. 

Many  of  these  texts  cover  the  entire  range  of  agriculture,  though 
necessarily  in  abbreviated  treatment.  There  are  those  who  believe 
that  when  agriculture  is  fully  introduced  as  a  secondary  school  sub- 
ject, it  will  consist,  as  in  college,  not  of  one  but  of  several  courses, 
each  with  its  distinctive  and  separate  text.  Such  a  text  the  author 
has  attempted  to  produce,  dealing  with  a  somewhat  restricted  and 
altogether  definite  field  —  the  soil  and  the  principal  crops  of  the 
northern  states. 

Most  books  heretofore  prepared  have  been  repositories  of  infor- 
mation to  be  studied  and  recited  like  other  subjects.  This  book 
is  distinctively  a  laboratory  manual,  the  belief  of  the  author  being 
that  the  student  should  be  led  to  study  agriculture  at  first  hand, 
and  that  his  impressions  as  well  as  his  knowledge  of  the  subject 
should  be  gained  through  the  most  intimate  personal  contact, 
remembering  always  that  it  is  the  science  of  agriculture  and  not 
its  art  or  handicraft  that  is  teachable  in  our  schools. 

The  author  is  eminently  qualified  to  treat  the  subject  he  under- 
takes. A  farmer  by  instinct,  with  a  long  and  successful  career 
as  a  teacher  in  secondary  schools,  he  took  the  agricultural  course 
at  the  University  of  Illinois  in  the  ripeness  of  full  maturity.  He 
has  since  that  time  given  his  exclusive  attention  to  the  adaptation 


vi  INTRODUCTION 

of  agriculture  to  secondary  instruction,  for  which  he  has  enjoyed 
exceptional  advantages  through  his  connection  with  the  agricultural 
extension  department  of  the  university.  He  therefore  brings  to 
this  book  not  only  the  instincts  of  a  farmer,  but  the  knowledge 
of  the  specialist  and  the  ripeness  of  judgment  of  a  mature  and 
successful  teacher. 

It  is  to  be  hoped  that  if  this  attempt  shall  prove  successful, 
either  this  author  or  others  equally  able  and  equally  willing  to 
perform  a  labor  of  love  will  extend  the  laboratory  manual  idea 
to  other  fields  of  this  most  fascinating  subject. 

E.   DAVENPORT. 


PREFACE 

Throughout  the  country  to-day  many  schools  of  secondary 
grade  are  expressing  a  desire  to  add  to  their  present  curricula  of 
studies  courses  of  instruction  in  agriculture ;  but  they  are  in  doubt 
as  to  the  character  and  extent  of  the  work  which  would  be  possi- 
ble or  advisable  for  them  to  offer  in  this  subject. 

While  a  considerable  number  of  elementary  books  in  agriculture 
has  been  written  in  recent  years,  few,  if  any,  of  them  were  pre- 
pared for  high  school  grades,  and  do  not  assume  to  compare  in 
the  character  of  matter  presented  or  in  their  thoroughness  of  the 
treatment  of  the  subject  with  texts  in  the  other  sciences  taught 
in  high  schools. 

Agriculture  is  now  recognized  as  embracing  so  large  a  field,  with 
so  many  different  divisions  and  special  interests,  that  no  single 
book  within  the  proper  bounds  of  a  high  school  text  could  pretend 
to  compass  the  whole  subject.  The  work  should  be  presented  in 
separate  courses  which  may  be  taken  by  classes  either  in  the  order 
of  their  natural  sequence,  or  a  selection  can  be  made  of  those 
courses  most  directly  related  to  the  particular  agricultural  interests 
of  the  communities  where  the  schools  are  situated. 

There  are  many  excellent  books  on  the  various  topics  included 
in  each  department  of  agriculture,  and  a  great  wealth  of  agricul- 
tural information  has  been  published  in  bulletin  form.  All  of 
this  is  available  matter  for  reference  and  should  be  of  much  value 
to  teachers  and  students  in  their  work;  but  as  yet  there  are  no 
texts  in  agriculture  that  have  been  prepared  to  meet  the  special 
needs  of  high  school  courses.     There  is  no  question,  however,  but 

vii 


viii  PREFACE 

that  the  urgent  demand  for  such  texts  will  call  forth  in  the  near 
future  many  good  books,  and  in  the  meantime  nmch  may  be  done 
with  the  material  now  at  hand  in  making  a  beginning  in  the  work 
of  secondary  school  agriculture. 

The  purpose  of  this  Manual  is  to  outline  a  course  of  study  in 
agriculture,  covering  at  least  one  year's  work,  which  shall  be  of 
high  school  grade,  and  shall  offer  training  in  sciences  comparable 
to  that  furnished  by  the  other  science  courses  in  good  high  schools. 

The  writer  believes  that  all  of  the  work  in  agriculture  taught 
in  our  high  schools  should  be  of  such  character  that  it  will  appeal 
to  the  practical  farmer  as  real  agriculture,  possible  of  application  to 
actual  conditions  and  closely  related  to  the  affairs  of  the  homes  and 
the  farms  of  the  community.  In  addition  to  this  it  should  possess 
such  educational  value,  both  in  its  content  and  in  its  opportunities 
for  training  in  scientific  methods  and  habits,  as  to  justify  its  place 
in  the  curriculum  of  any  good  high  school. 

The  work  as  outlined  in  this  course  is  confined  to  studies  in 
soils  and  crop  production.  Since  the  growing  of  crops  is  the  basis 
of  all  farming  operations  and  every  form  of  agriculture  is  inti- 
mately associated  with  the  cultivation  of  the  soil,  it  seems  best 
to  make  this  work  the  foundation  for  the  courses  in  agriculture 
to  be  taught  in  high  schools. 

Then,  following  this,  a  study  of  the  breeds  and  types  of  the 
most  important  farm  animals  and  something  of  the  laws  of  breed- 
ing and  improvement  of  stock,  a  study  of  methods  of  feeding,  the 
principles  of  nutrition  and  a  comparison  of  the  nutrient  values 
of  the  different  foodstuffs  produced  and  used  on  the  farm,  the 
symptoms,  causes,  treatment,  and  prevention  of  the  more  common 
ailments  of  domestic  animals,  the  composition  and  care  of  milk 
and  the  testing  of  milk  for  butter  fat,  a  study  of  the  more  com- 
mon insect  pests  and  plant  diseases  with  the  proper  treatment  for 
each,  and  the  preparation  of  the  different  insecticides  and  fungi- 


PREFACE  ix 

cides,  —  such  topics  as  these  might  be  selected  as  material  for 
the  work  of  a  second  course. 

The  plan  of  work  suggested  in  this  Manual  includes  recitations 
following  the  reading  and  discussion  of  the  portions  of  texts  and 
bulletins  treating  each  topic  as  it  is  taken  up  combined  with  exer- 
cises in  the  laboratory  and  supplemented  wherever  possible  with 
pot-culture  work  and  field  experiments. 

Many  of  the  laboratory  exercises  are  the  same  that  are  used 
in  the  courses  in  agricultural  colleges,  for  it  is  believed  that  the 
work  in  high  school  agriculture  should  hold  the  same  relation  to 
college  agriculture  as  exists  in  the  case  of  the  other  high  school 
sciences,  —  botany,  zoology,  physics,  chemistry,  and  in  mathe- 
matics and  languages,  —  with  the  expectation  that  many  high 
schools  will  be  able  to  do  work  in  agriculture  for  which  college 
credits  can  be  allowed. 

In  Part  I,  Exercise  1  is  borrowed  from  Soil  Physics  Laboratory 
Guide  by  Professors  Stevenson  and  Schaub  of  Iowa  State  College. 
Exercises  2  to  20  inclusive  are  taken  from  Laboratory  Manual 
for  Soil  Physics  by  Professor  J.  G.  Mosier  of  the  University  of 
Illinois.  In  a  few  instances  they  have  been  slightly  altered  to 
adapt  them  to  the  purposes  of  the  book. 

In  Part  II,  page  52,  acknowledgment  is  made  to  Dr.  C.  G. 
Hopkins  and  Professor  J.  H.  Pettit  of  the  University  of  Illinois 
for  material  used. 

In  the  work  with  corn  the  author  has  drawn  very  freely  from 
the  admirable  circular.  Studies  of  Corn  and  Lts  Uses,  prepared  by 
Professor  Fred  H.  Rankin  of  the  University  of  lUinois. 


CONTENTS 


PART   I.     STUDIES   ABOUT   SOILS 


PAGE 


I.     Physical  Composition  of  the  Soil     ...         1 
Exercise  1.     Examination  of  Soil  Particles  with 
Microscope     .......         2 

II.     Moisture  Relations  of  Soils     ....         3 

Exercise  2.     Determination  of  Total  Moisture  in 

Samples  of  Field  Soils      .....         4 

III.  Different  Forms  of  Soil  Moisture   ...         6 

Exercise  3.     Determination  of  Capillary  Moisture 

in  Field  Soils  .......         8 

IV.  Soil  Temperature  and  its  Control  ...    9 

Exercise  4.     Effect  of  Drainage  on  Soil  Tempera- 
ture       ........       10 

V.     Influence  and  Control  of  Color  of  Soils       .       10 

Exercise  5.     Effect  of  Color  of  Soil  on  Temperature       1 1 
VI.     Effect  of  Lime  on  Heavy  Soils         .         .         .12 

Exercise  6.  Determination  of  the  Effects  of  Lime 
on  Plastic  Soils        .         .         .         .         .         .13 

Exercise  7.     Weight  of  Soils        .         .         .         .14 

Exercise  8.  Determination  of  the  Apparent  Spe- 
cific Gravity  of  Surface  Soil  under  Field  Condi- 
tions      .         .         .         .         .         .         .         .15 

Exercise  9.  Determination  of  the  Weight  of  Soil 
per  Acre-foot  .         .         .         .         .         .         .15 

Exercise  10.  Determination  of  Specific  Gravity  of 
Soils.     Volumetric  Method       .         .         .         .16 

xi 


xii  CONTENTS 

VII.     Questions  concerning  the  Weight  of  Soils 
VIII.     Porosity  of  Soils     ..... 

Exercise  11.     Determination  of  Porosity  —  First 
Method         ...... 

IX.     The  Organic  Matter  in  Soils 

Exercise  12.     Determination  by  Ignition  of  the 
Loss  of  Organic  Matter  by  Cropping 

X.     The  Water-retaining  Power  of  Soils     . 
Exercise  13.     Power  of  Soils  to  retain  Water 

XI.     Effect  of  Compacting  the  Soil 

Exercise  14.     Power  of  Compact  Soils  to  retain 
w  ater  ...«••• 

XII.     How  Organic  Matter  in  Soils  affects  their 
Water-holding  Power 
Exercise  15.     Effect  of  Organic  Matter  on  Reten 
tion  of  Water         ..... 

XIII.  Capillary  Movement  of  Soil  Moisture 

Exercise  16.     A  Study  of  the  Capillary  Action  of 
Soils     ....... 

XIV.  A  Common  Mistake  in  Applying  Manure 

Exercise  17.    Effect  of  Organic  Matter  on  Rise  of 
Water  in  Soils       ..... 

XV.     The  Farmer's  Control  of  Soil  Moisture 

Exercise  18.     Effect  of  Soil  Mulches  on  Evapora 
tion  of  Water  from  Soils  .         .         . 

XVI.     Mulches  of  Various  Materials 

Exercise  19.     Effect  of  Artificial  Mulches  upon 
Evaporation  of  Water  from  Soils 


CONTENTS 


XIU 


PAGE 


XVII.     Improvement  of  Heavy  Soils  by  Use  of  Farm 

Manure  .......       35 

Exercise  20.  The  Effect  of  Organic  Matter  on 
Baking  of  Clay  Soils  .         .         .         .         .37 


PART  II.  STUDIES  ABOUT  CROPS 

XVIII.     What  Foods  Plants  Use  and  how  they  are 

Obtained 39 

Exercise  21.  To  show  that  Certain  Plant 
Foods  are  Essential  Preparation  of  Pot  Cul- 
tures        .......       44 

XIX.     Farming  in  Four-gallon  Pots       ...       46 
Exercise  22.       Applications  of  Plant  for  Crop 
Production         ......       49 

XX.     Experiment  Field  Work  for  High  Schools        50 
Exercise  23.     Plot-culture  Tests  to  determine 

Plant  Food  Requirements  of  the  Soil    .         .       52 

XXI.     Questions  relating  to  the  Seeding  of  Crops       55 
Exercise    24.     Crop    Production :    Oats.      To 
determine    what   Amount  of  Seed  per  Acre 
gives  Best  Results      .         .         .         .         .56 

XXII.     Methods  of  Sowing  Grains  .         .         .         .57 
Exercise  25.       Test  of  Drilling  versus  Broad- 
casting     .......       58 

Exercise  26.     Treating  Seed  Oats  for  Smut      .       60 

XXIII.  Special  Treatment  of  Seed  ...       58 

XXIV.  Studies  with  Corn 62 

Exercise  27.       Crop    Production :    Corn.      To 

determine  how  Close  to  plant  Corn       .         .       63 


XIV 


CONTENTS 


PAOB 

XXV.     Problems  in  Cultivating  Corn  ...  64 
Exercise  28.     To  show  Effects   of  Different 

Methods  of  Tillage 65 

XXVI.     How  Moisture  may  be  saved  for  the  Corn 

Crop 66 

Exercise  29.  Determination  of  the  Water 
Content  of  the  Soil  for  Each  Plot  for  Exer- 
cise 28 -.67 

XXVII.     Growth  of  Corn  Roots       .         .         .        .67 

Exercise  30.     A  Study  of  Corn  Roots   .         .  69 
Exercise  31.      Corn   Breeding :    Selection   of 

Seed 71 

Exercise  32.     Practice  in  Detasseling    .         .  73 

Exercise  33.    Experiment  in  Hand  Pollination  74 

XXVIII.     Observation  Studies  in  the  Cornfield     .  75 

Exercise  34.     Field  Work  with  Corn     .         .  76 

Exercise  35.     Studies  of  an  Ear  of  Corn         .  78 

XXIX.     Judging  and  Scoring  Corn         ...  82 

Corn  Score  Card  ......  83 

.  88 


Exercise  36. 


Testing  Corn  for  Seed 


MANUAL   OF   AGRICULTURE 

PART  I.  —  STUDIES   ABOUT   SOILS 

I.  —  Physical  Composition  of  the  Soil 

"  The  soil  is  not  a  mere  inert  mixture.  Its  parts 
have  shape  and  size  and  arrangement,  as  well  as  being 
merely  composed  of  certain  substances.  All  of  these 
parts  have  been  separately  formed,  moved,  and  assorted, 
and  then  laid  down  together  as  we  find  them ;  and, 
moreover,  they  are  not  even  yet  at  rest,  but  are  always 
taking  new  forms  and  new  places  and  making  new 
partnerships,  entailing  a  never-ending  series  of  myster- 
ies. From  the  soil  all  things  come ;  and  into  it  all 
things  at  last  return ;  and  yet  it  is  always  new  and 
fresh  and  clean,  and  always  ready  for  new  generations. 
This  soft,  thin  crust  of  the  earth  —  so  infinitesimally 
thin  that  it  cannot  be  shown  in  proper  scale  on  any 
globe  or  chart  —  supports  all  of  the  countless  myriads 
of  men  and  animals  and  plants,  and  has  supported  them 
for  countless  cycles,  and  will  continue  to  yet  support 
for  other  countless  cvcles.  In  view  of  all  this  achieve- 
ment,  it  is  not  strange  that  we  do  not  3^et  know  the  soil 
and  understand  it;  and  we  are  in  mood  to  be  patient 

1 


2  MANUAL  OF  AGRICULTURE 

with  our  shortcomings."  —  Bailey,  Cyclopedia  of 
American  Agriculture. 

The  soil,  in  an  agricultural  sense,  is  always  a  mixture 
of  inorganic  and  organic  matter.  If  either  of  these 
materials  be  lacking,  it  is  not  a  true  soil.  The  organic 
matter  is  composed  of  bits  of  decaying  plant  or  animal 
substances — usually  both.  Disintegrated  and  pulver- 
ized rock  constitute  the  inorganic  portion  of  the  soil. 
Soil  particles  differ  in  size,  form,  and  arrangement,  in 
weight  and  color.  In  most  cultivated  soils  the  in- 
organic material  forms  from  85  per  cent  to  95  per  cent 
by  weight  of  the  mass.  A  sandy  soil  is  usually  defi- 
cient in  organic  matter,  while  peaty  soils  contain  an 
excess  of  it. 

The  object  of  Exercise  1  is  to  help  the  student  to  get 

a  correct  conception  of  the  physical  composition  of  some 

of  the  common  types  of  soil. 

Keferences  :  King,  The  Soil,  pp.  27-76.  Fletcher,  Soils,  pp.  3- 
27,  46-74.  Snyder,  Soils  and  Fertilizers^  pp.  9-56.  Warington, 
Physical  Properties  of  Soil,  pp.  1-50. 

Exercise  1 

Examination  of  Soil  Particles  with  Microscope 

1.  —  Place  upon  a  glass  slide  a  few  grains  of  coarse  sand  and 
examine  carefully  with  the  low  power  of  the  microscope,  noting 
these  points :  — 

(a)    Color  —  white,  gray,  brown,  red,  or  black. 

(p)    Shape  —  angular,  rounded,  or  irregular. 

(c)  Simple  or  compound  grains. 

(d)  Size  —  coarse,  medium,  or  fine. 


STUDIES  ABOUT  SOILS  3 

II.  —  In  the  same  way  study  other  types  of  soils  —  fine  sand, 
loam,  silt,  clay,  loess,  and  peat. 

On  separate  sheets  make  drawings  of  a  number  of  particles  of 
each  kind  of  soil,  and  describe  them  with  reference  to  (a),  (6),  (c), 
and  (c^). 

II. — Moisture  Relations  of  Soils 

The  study  of  the  moisture  relations  of  soils  as  af- 
fected by  differences  in  their  physical  constitution,  or 
by  differences  in  their  texture  due  to  the  character  of 
the  cultivation  which  they  have  received,  is  probably 
the  largest  and  most  interesting  problem  in  soil  physics. 

The  capacity  of  a  soil  to  absorb  water  in  large 
amounts,  to  hold  it  in  a  form  that  does  not  prevent  the 
free  development  of  the  roots  of  plants  to  a  sufficient 
depth,  and  the  ability  to  lift  this  water  from  below,  as 
the  needs  of  the  growing  crops  demand  it,  up  into  the 
zone  occupied  by  their  roots,  are  the  ideal  conditions  of 
the  soil  which  the  skillful  farmer  tries  to  secure.  The 
study  of  soil  physics  is  to  help  him  understand  the 
principles  which  control  these  conditions. 

In  Exercise  2  the  objects  are:  — 

(1)  To  show  that  the  moisture  content  of  a  soil  de- 
pends in  part  upon  its  surface  conditions,  i.e.  what 
demands  the  crop  growing  on  it  is  making  for  water, 
and  what  the  character  is  of  the  surface  cultivation. 

(2)  To  determine  the  relative  amounts  of  water 
stored  in  the  ground  at  different  depths,  —  in  strata 
commonly  designated  as  surface^  subsurface^  and  suh- 
8oiL 


4  MANUAL  OF  AGRICULTURE 

The  determination  of  the  moisture  content  of  a  soil 
is  a  very  simple  process,  and  its  frequent  use  on  the 
farm  would  pay  for  the  trouble  it  costs.  In  this  way 
one  may  easily  test  the  difference  in  the  amounts  of 
water  in  the  ground  at  different  depths  due  to  fall 
versus  spring  plowing,  to  early  versus  late  spring  plow- 
ing, to  differences  resulting  from  various  kinds  of  sur- 
face cultivation  and  surface  mulching,  etc. 

All  of  the  work  should  be  done  carefully  and  accu- 
rately in  every  exercise.  Otherwise  it  has  absolutely 
no  value  in  results  obtained  and,  besides,  is  very  bad 
training. 

References  :  King,  The  Soil,  pp.  154-170.  Fletcher,  Soils,  pp.  75- 
84.  Snyder,  Soils  and  Fertilizers,  pp.  22-25.  Warington,  Physical 
Properties  of  Soil,  pp.  51-57,  64-73. 


Exercise  2 

Determination  of  Total  Moisture  in  Samples  of  Field  Soils 

According  to  directions  given  below,^  collect  samples  of  soils  from 
(1)  an  old  sod,  (2)  between  the  rows  of  corn,  (3)  tilled  ground 
where  no  crop  is  growing.  Take  the  samples  in  each  case  from 
the  surface,  subsurface,  and  subsoil. 

'  Directions  for  collecting  soil  samples :  For  this  purpose  a  pne-and 
a-half  or  two-inch  auger,  with  an  extension  making  it  40  inches  long,  is 
used.  In  collecting  samples  for  moisture  determinations,  expose  the  soil 
as  little  as  possible  to  the  air  before  putting  in  jars.  Collect  the  surface 
soil  to  the  depth  of  the  plow  line,  usually  about  7  inches.  After  this 
part  of  the  sample  is  removed,  the  hole  is  enlarged  sufficiently  so  that 
the  subsurface  soil  may  be  taken  without  coming  in  contact  with  the 
surface  soil.     Take  the  subsurface  sample  to  the  subsoil  line  as  indi- 


STUDIES  ABOUT  SOILS  5 

Mark  and  carefully  weigh  six  soil  pans.  Run  all  experiments 
in  duplicates  for  the  sake  of  greater  accuracy. 

Place  in  each  soil  pan  100  grains  of  the  soil  sample  to  be 
studied,  taking  the  weights  rapidly  to  prevent  loss  by  evaporation. 
Put  them  in  the  drying  oven  for  five  hours  at  a  temperature  of 
100°  to  110°  C.  Cool  to  room  temperature  and  weigh  at  once. 
The  loss  in  weight  represents  the  total  moisture  content  of  the 
soil. 

If  three  students  work  together,  one  might  take  the  surface,  an- 
other the  subsurface,  and  the  third  the  subsoil.  Then  compare 
residts. 

Tabulate  the  results  as  follows  :  — 

Total  Moisture  Determination 


Kind  of 

Soil. 


Pan 

No. 


Wt.  of 
Pan. 


Wt.  of 

Soil. 


Wt.  of 

Soil  and  Pan, 


Wt.  of  Dry 

Soil  and  Pan, 


Wt.  of 
Dry  Soil. 


Loss 
of  wt. 


Per  Cent 
Moisture. 


Gated  by  the  change  in  color,  texture,  and  physical  composition.  Com- 
monly this  line  is  found  at  a  depth  of  16  to  20  inches.  Enlarge 
and  clean  out  the  hole  as  before.  Since  the  change  from  subsurface 
to  subsoil  is  not  a  sharp  line,  but  usually  somewhat  gradual,  we  dis- 
card about  two  inches  of  the  intermediate  mixture.  The  subsoil  is  then 
collected  to  a  depth  of  40  inches,  if  possible. 

In  some  soils  the  subsurface  layer  may  be  absent,  the  subsoil  being 
reached  by  the  plow,  while  in  others,  as  in  peaty  and  sandy  soils,  no 
true  subsoil  may  be  found  within  40  inches  of  the  surface.  In  such 
cases  only  two  samples  are  taken. 


6  MANUAL   OF  AGRICULTURE 

State  the  weather  conditions  when  the  samples  were  collected 
and  the  amount  of  the  rainfall  during  the  previous  week. 

Which  soil  had  largest  water  content  ?  Which  had  the  least  ? 
What  is  the  explanation  ?  Was  most  water  found  in  the  surface, 
subsurface,  or  subsoil  ? 

III.  —  Different  Forms  of  Soil  Moisture 

Most  of  the  water  in  the  soil  comes  from  the  rains 
and  snows  that  fall  on  the  surface  of  the  ground.  A 
part  of  what  falls  is  quickly  evaporated  before  it  soaks 
into  the  ground.  Another  portion  forms  into  rills  and 
flows  over  the  surface  joining  larger  streams  and  usually 
carrying  in  its  currents  more  or  less  of  the  richest  par- 
ticles of  the  soil,  to  be  eventually  lost  in  the  sea.  The 
amount  of  water,  with  its  burden  of  soil,  that  is  thus 
lost  to  the  farmer  depends  largely  upon  the  topography 
of  the  land  and  the  condition  of  its  surface.  In  a  hilly 
country,  and  wherever  the  upper  soil  is  packed  and 
bare  of  vegetation,  the  surface  wash  is  likely  to  be 
serious. 

The  remaining  part  of  the  rainfall  and  melting  snows 
graduall}^  sinks  into  the  ground,  and  is  either  absorbed 
by  the  soil  particles  and  held  as  a  film  over  their  sur- 
faces, or  it  percolates  down  through  the  cracks  and 
crevices  in  the  soil,  obeying  the  law  of  gravity,  until 
it  reaches  the  level  of  standing  water,  commonly  spoken 
of  as  the  water  table. 

Of  all  these  divisions  of  the  water  which  comes  to  the 
earth  as  rain  and  snow,  it  is  only  the  portion  that  soaks 
into  the  ground  and  is  held  as  film  water  around  the 


STUDIES  ABOUT  SOILS  7 

soil  particles  which  is  directly  concerned  in  supplying 
growing  plants  with  moisture,  and  for  this  reason  is  of 
greatest  interest  to  the  agriculturist.  This  moisture 
is  called  capillary  moisture  because  it  moves  in  all  direc- 
tions through  the  interstices  between  the  soil  particles 
by  the  force  of  capillary  attraction,  just  as  oil  in  a  lamp 
flows  upward  through  the  wick. 

But  not  all  of  the  film  water  about  the  soil  grains  is 
free  to  move  under  the  influence  of  capillary  attraction. 
Adhering  to  the  surfaces  of  all  solids  of  atmospheric 
temperature  is  an  exceedingly  thin  film  of  moisture 
which  can  be  expelled  only  by  exposure  to  a  high  de- 
gree of  heat.  This  film  of  water  is  known  as  hygro- 
scopic moisture^  and  can.be  driven  off  from  the  soils  only 
by  keeping  them  in  a  drying  oven  at  a  temperature  of 
about  105°  C.  for  five  or  six  hours.  Roots  of  plants  are 
unable  to  overcome  the  adhesive  power  which  holds 
this  film  of  moisture  to  the  soil  particles.  On  the 
other  hand,  the  greater  part  of  the  layer  of  moisture 
surrounding  the  soil  grains  is  held  so  loosely  that  the 
plant  roots  can  absorb  it  readily  by  a  force  called  osmo- 
sis^ and  when  exposed  to  the  air  it  is  carried  off  by 
evaporation. 

In  Exercise  2  the  total  moisture  content  of  the  soil 
was  determined  by  using  the  drying  oven  and  expelling 
both  the  capillary  and  the  hygroscopic  moisture  at  the 
same  time.  The  residue  remaining  in  the  soil  pans  is 
water-free  soil,  and  this  is  taken  as  the  basis  in  all  com- 
putations and  data  relating  to  soils,  because  it  is  the 
only  uniform  condition  that  can  be  secured. 


8  MANUAL   OF  AGRICULTURE 

In  Exercise  3  only  a  determination  of  the  capillary 
moisture  is  sought,  and  this  requires  merely  an  exposure 
of  the  soils  to  the  air  until  a  constant  weight  is  reached, 
that  is,  until  all  the  capillary  moisture  has  evaporated. 

References  :  King,  The  Soil,  pp.  173-178.  Fletcher,  Soils,  pp. 
29-31,  87-90.     Warington,  Physical  Properties  of  Soil,  pp.  92-107. 

Exercise  3 

Determination  of  Capillary  Moisture  in  Field  Soils 

Use  soils  from  the  same  samples  taken  for  Exercise  2.  (The 
jars  should  be  kept  tightly  sealed  except  when  the  samples  are 
being  weighed  out.  Mix  the  soils  well  by  thoroughly  shaking  the 
jars  before  opening.) 

Number  and  weigh  carefully  6  soil  pans.  Place  in  each  100 
grams  of  soil,  running  duplicates  of  surface,  subsurface,  and  sub- 
soil. With  a  glass  rod  carefully  break  up  all  lumps  and  spread  the 
soU  evenly  over  bottom  of  pan.  Let  the  soils  dry  at  room  tem- 
perature, and  take  the  weights  every  24  hours.  When  the  weight 
becomes  constant,  the  loss  indicates  the  amount  of  capillary  mois- 
ture. 

Compute  the  percentage  of  capillary  moisture  in  each  sample  on 
the  basis  of  the  water-free  soil  as  found  in  Exercise  2.  Tabulate 
the  results  as  in  the  previous  exercise. 

Notice  that  the  difference  between  the  total  moisture  content  and 
the  amount  of  capillary  moisture  in  a  sample  represents  approxi- 
mately the  hygroscopic  moisture  of  that  soil. 

How  does  this  compare  in  amount  with  the  per  cent  of  capillary 
moisture  ? 

Axe  the  amounts  about  the  same  for  all  of  the  soils  and  in  the 
same  relative  order  for  surface,  subsurface,  and  subsoil  1 


STUDIES  ABOUT   SOILS  9 

IV.  —  Soil  Temperature  and   its  Control 

A  warm  soil  is  superior  to  one  that  is  cold  for  crop 
production.  For  each  kind  of  crop  there  is  a  minimum 
temperature  below  which  its  seeds  will  not  germinate. 
There  is  also  for  every  kind  of  plant  an  optimum  tem- 
perature for  growth.  A  plant  produced  from  a  seed 
that  has  germinated  in  a  soil  too  cold  for  the  plant  to 
start  with  a  vigorous  growth  becomes  stunted  and  never 
reaches  maximum  development.  The  various  forms  of 
microorganisms  and  chemical  processes  in  the  soil,  upon 
whose  activities  the  fertility  of  soils  is  largely  depend- 
ent, require  a  warm  environment  for  their  best  work. 

The  gain  of  a  few  days  at  the  beginning  of  the  sea- 
son, for  many  crops,  constitutes  a  large  factor  in  their 
success. 

Most  farmers  do  not  realize  that  soil  temperature  is 
a  thing  over  which  they  may  have  much  control,  and 
probably  a  majority  of  them  would  think  that  the  dif- 
ference of  a  few  degrees  is  of  too  little  consequence  to  be 
considered.  But  the  scientist,  the  engineer,  the  pro- 
fessional man,  the  manufacturer,  and  the  business  man 
have  all  been  trained  to  appreciate  the  importance  of 
every  factor  that  enters  into  their  work.  It  is  here 
that  the  training  of  the  farmer  has  been  especially 
weak;  and  it  is  the  province  of  the  study  of  the  science 
of  agriculture  to  correct  this  fault  in  his  training  and 
teach  him  how  he  may  control  conditions  which  before 
he  had  supposed  were  beyond  his  power  to  influence. 

An  undrained  or  wet  soil  is  cooler  than  a  dry  one. 


10  MANUAL  OF  AGRICULTURE 

because  there  is  so  much  greater  evaporation  of  mois- 
ture from  its  surface,  and  the  amount  of  heat  required 
to  vaporize  a  pound  of  water  is  very  considerable.  It 
requires  four  or  five  times  as  many  heat  units  to  raise 
a  given  weight  of  water  1°  F.  as  are  needed  for  the 
same  amount  of  dry  soil.  The  object  in  Exercise  4  is 
to  demonstrate  and  impress  these  facts. 

References  :  King,  The  Soil,  pp.  218-227,  234-238.  Fletcher, 
Soils,  pp.  33-34.    Warington,  Physical  Properties  of  Soil,  pp.  165-178. 

Exercise  4 

Effect  of  Drainage  on  Soil  Temperature 

Make  two  wooden  boxes  3x4  feet  and  6  inches  deep,  building 
one  water-tight  and  the  other  loose  enough  to  allow  the  water  to 
drain  off.  Fill  each  box  with  the  same  kind  of  soil,  and  apply  the 
same  amounts  of  water  till  drainage  begins  in  the  loose  box.  The 
boxes  should  stand  in  the  open  air,  where  evaporation  is  free.  After 
drainage  has  ceased,  take  the  temperature  of  the  soils  in  each  box 
hourly,  on  a  clear  day,  at  the  depths  of  1,  2,  and  4  inches. 

Give  explanations  for  the  differences  in  temperature. 

Why  is  clay  called  a  cold  soil,  and  sand  warm  ? 

V.  —  Influence  and  Control  of  Color  of  Soils 

The  color  of  the  surface  soil  has  a  marked  influence 
on  its  temperature.  Between  soils  of  dark  color  and 
those  of  a  light  hue  there  is  often  found  a  difference  of 
5°  to  10°  F.  at  a  depth  of  2  to  5  inches.  For  many  crops 
early  in  the  season  this  is  a  matter  of  considerable  im- 
portance.     Soils  containing  large  amounts  of  organic 


STUDIES  ABOUT  SOILS  11 

matter  are  dark  colored.  Through  careless  or  unwise 
cultivation,  soils  gradually  grow  lighter  colored.  The 
farmer's  control  of  these  conditions  comes  mainly 
through  the  use  of  barnyard  manure  and  the  plowing 
under  of  green  crops.  In  Exercise  5  there  is  an  op- 
portunity to  demonstrate  two  things  :  — 

(1)  Dark-colored  soils  absorb  a  larger  proportion  of 
heat  from  the  rays  of  the  sun  than  do  light-colored  soils. 

(2)  Seeds  will  germinate  more  quickly  and  plants 
grow  more  rapidly  in  soils  of  dark  color  than  in  those 
of  light  color. 

Keferences  :  King,  The  Soil,  p.  230.  Fletcher,  Soils,  pp.  34-36. 
WaringtoD,  Physical  Properties  of  Soil,  pp.  161-164. 

Exercise  5 

Effect  of  Color  of  Soil  on  Temperature 

Fill  a  wooden  tray  6  feet  long,  3  feet  wide,  and  6  inches 
deep  with  well-pulverized  soil  of  a  light  color.  By  a  wire  drawn 
taut  across  the  tray  lengthwise,  divide  the  surface  into  halves. 
Then,  by  other  lines  drawn  crosswise  of  the  tray,  divide  each  half 
into  6  equal  plots.  Designate  the  corresponding  plots  in  each  half 
by  the  same  letter,  and  in  each  two  plots,  similarly  marked,  plant 
the  same  kind  and  number  of  seeds,  using  corn,  peas,  beans,  oats, 
wheat,  and  rye.  In  one  half  of  the  tray  bury  the  seeds  J  inch 
deep  in  the  soil ;  in  the  other  half  cover  them  with  i  inch  of  the 
light-colored  earth, ^  and  then  add  \  inch  of  some  dark  soil  or  of 
soot,  so  that  the  seeds  in  every  plot  are  covered  to  the  same  depth. 

1  If  it  is  not  easy  to  obtain  a  soil  that  is  quite  light  or  quite  dark  in 
color,  the  soil  in  half  of  the  tray  can  be  whitened  by  a  thin  dressing  of 
lime  or  chalk  dust,  and  the  other  half  darkened  by  soot. 


12  MANUAL   OF  AGRICULTURE 

(a)  Every  morning  and  evening  observe  the  number  of  plants 
showing  above  the  surface  on  each  plot  and  carefully  record  them, 
comparing  results  in  the  light-colored  soil  with  those  in  the  dark 
earth. 

(b)  Choose  a  clear  day  and  make  observations  of  the  tempera- 
tures of  the  soils  in  the  two  halves  of  the  tray.  Insert  thermome- 
ters in  the  soil  to  the  depths  of  1,  2,  and  4  inches  in  both 
the  light-colored  earth  and  the  dark-colored  earth,  and  take  hourly 
readings  from  7  a.m.  to  5  p.m.  Keep  all  parts  of  the  tray  equally 
moist. 

Each  student  may  look  after  the  planting  of  a  single  plot,  but 
he  must  make  observations  on  all  plots  in  the  tray  and  hand  them 
in  in  tabular  form. 

Which  tray  shows  the  higher  temperature  ?     Why  ? 

Why  can  you  see  the  corn  rows  on  the  low,  black  land  sooner 
after  planting  than  upon  the  higher,  light-colored  soil  ? 

VI.  —  Effect  of  Lime  on  Heavy  Soils 

One  of  the  most  difficult  problems  that  many  farmers 
have  to  deal  with  in  the  cultivation  of  their  land  is  how 
to  handle  their  clay  soils  and  fine  silts  so  that  the 
proper  texture  of  the  soil  shall  be  preserved. 

A  peculiarity  of  these  soils  if  they  are  stirred  when 
too  moist,  is  that  they  become  pasty  and  run  together  so 
that  on  drying  they  are  hard  like  cement.  This  quality 
is  due  to  the  fineness  of  the  soil  grains,  which  are  so 
small  that  if  they  are  packed  closely  together  the  in- 
terstices between  them  are  not  large  enough  for  either 
water  or  air  to  penetrate.  When  a  soil  is  in  this  con- 
dition, it  is  of  little  value  for  farming  purposes.    A  soil 


STUDIES  ABOUT  SOILS  13 

is  said  to  be  in  good  tilth  when  the  individual  soil 
grains  are  massed  together  in  crumbs  or  granules  about 
the  size  of  timothy  seed.  Now  it  has  been  discovered 
that  the  action  of  lime  upon  a  clay  soil  is  to  cause  the 
fine  particles  to  flocculate  and  assume  a  crumbly  tex- 
ture, making  the  soil  lighter  to  till  and  more  easily 
drained. 

The  object  in  Exercise  6  is  to  demonstrate  to  the 
student  the  possibility  of  controlling  the  conditions  of 
texture  in  fine-grained  soils  by  the  application  of  lime. 

References  :  King,  The  Soil,  p.  30.  Warington,  Physical  Prop- 
erties of  Soils,  pp.  30-33. 

Exercise  6 

Determination  of  the  Effects  of  Lime  on  Plastic  Soils 

Two  students  may  work  together  in  this  experiment. 

Weigh  out  six  300-gram  samples  of  the  clay  soU,  using  them 
as  follows  :  to  sample 

No.  1,  check,  add  no  lime. 

No.  2,  add  .5  gram  of  air-slacked  lime. 

No.  3,  add  1  gram  of  air-slacked  lime. 

No.  4,  add  5  grams  of  air-slacked  lime. 

No.  5,  add  10  grams  of  air-slacked  lime. 

No.  6,  add  10  grams  sand. 

Mix  each  sample  thoroughly  in  a  soil  pan  with  the  lime,  and  add 
just  enough  water  to  make  plastic. 

FiU  the  semicircular  molds,^  first  placing  in  each  a  damp,  thin 

1  It  may  be  easier  to  make  molds  with  dimensions  4"  x2"  x  1". 

The  test  can  be  made  by  suspending  from  the  middle  of  the  stick  a 
bucket  into  which  sand  is  slowly  poured  until  the  weight  is  secured 
which  is  necessary  to  break  the  stick. 


14  MANUAL   OF  AGRICULTURE 

cloth  to  facilitate  the  removal  of  the  clay.  Make  duplicates  of  each 
sample,  being  careful  to  compress  each  to  the  same  degree.  Place 
on  a  cloth  in  a  soil  pan  and  dry  in  an  oven  for  five  hours  at  105°  C. 

Test  the  strength  of  each  brick  by  supporting  the  ends  so  as  to 
allow  just  three  inches  between  points  of  support.  Hang  a  weight 
pan  in  middle  of  the  brick,  and  determine  the  weight  necessary  to 
break  each  one. 

Express  data  in  tabular  form. 

Explain  the  effect  of  lime. 

Why  does  the  sand  not  have  as  much  effect  as  the  lime  on  the 
breaking  strength  ? 

EXEECISE   7 

Weight  of  Soils 

Determine  the  cubic  contents  of  a  box  the  three  dimensions  of 
which  are  from  6  to  1 2  inches.  Take  the  weight  of  the  box  and 
contents  when  filled  with  different  air-dry  soils,  viz.  sand,  clay, 
loam,  loess,  and  peaty  soil.  In  filling  the  box,  do  not  compact  the 
soil.  From  the  data  obtained,  compute  the  weight  per  cubic  foot 
of  each  soil. 

Calculate  the  weight  of  an  acre  of  each  soil  to  the  usual  depth 
of  the  plow  line,  7  inches. 

The  weight  of  a  cubic  foot  of  water  is  62.42  pounds.  The  ap- 
parent specific  gravity  of  each  soil  tested  may  be  found  as  follows  : — 

Volume  wt.  of  soil  a         -^  v      ^     •? 
^ =  apparent  specijic  gravity  of  soil. 

Volume  wt.  of  water 

In  this  computation  the  waiter  free  weight  of  the  soil  should  be 
used.  To  do  this,  determine  the  per  cent  of  hygroscopic  moisture 
in  a  small  sample  of  this  soil.  The  weight  of  any  given  volume 
of  this  soil  divided  by  one  plus  the  rate  per  cent  of  the  moisture, 
will  give  as  a  quotient  the  weight  of  water-free  soil. 


STUDIES  ABOUT   SOILS  15 

Exercise  8 

Determination  of  the  Apparent  Specijic  Gravity  of  Surface 

Soil  under  Field  Co7iditions 

Take  a  tube  provided  for  the  purpose,  and  force  it  into  the 
ground  to  the  depth  of  six  inches.  Remove  soil  to  a  weighed  pan, 
and  dry  in  the  oven  at  105°  C.  for  at  least  ten  hours.  Find  weight 
of  volume  of  water  equal  to  that  of  the  soil  taken,  and  divide  the 
weight  of  the  water-free  soil  by  this.  The  result  will  be  the  ap- 
parent specific  gravity. 

The  apparent  specific  gravity  of  soils  in  the  field  may  be  taken 
as  an  approximate  indication  of  the  tilth  of  the  soils,  since  the 
better  the  tilth  the  less  will  be  the  apparent  specific  gravity  for 
the  same  kind  of  soil.  This  is  due  to  the  fact  that  soils  in  good 
tilth  are  looser  on  account  of  the  presence  of  organic  matter  and 
better  granulation.  The  apparent  specific  gravity  of  a  continu- 
ously cropped  soil  is  higher  than  one  having  proper  rotations. 
Why? 

What  would  be  the  approximate  weight  of  a  cubic  foot  of  soil 
under  the  above  conditions  1 


Exercise  9 

Determination  of  the   Weight  of  Soil  per  Acre  foot 

Drive  into  the  soil  a  brass  tube  (8"  long  and  about  3"  in  diam- 
eter, sharpened  at  its  lower  edge)  until  the  top  is  level  with  the 
surface. 

Dig  away  the  soil  around  the  tube ;  empty  the  tube  upon  a 
piece  of  oilcloth  and  transfer  the  soil  to  a  Mason  jar ;  carefully  drive 
the  tube  down  again,  and  thus  obtain  a  sample  of  the  succeeding 


16  MANUAL  OF  AGRICULTURE 

eight  inches.  Repeat  this  operation  until  eight-inch  samples  of 
the  soil  have  been  secured  to  any  desired  depth.  Carefully  weigh 
each  sample.  Determine  the  total  moisture  in  100  grams  of  soil 
from  each  depth,  and  from  these  data  determine  the  weight  of  the 
water-free  soil.  Calculate  in  cubic  inches  the  content  of  the  tube. 
Calculate  the  weight  of  an  acre  of  soil  to  the  depth  at  which 
each  sample  was  taken.     Tabulate  the  results. 


Exercise  10 

Determination  of  Specific  Gravity  of  Soils.     Volumetric 

MetJiod 

Determine  exactly  the  amount  of  water  required  to  fill  the 
measuring  flask  to  the  50  cubic  centimeter  mark  by  using  a 
burette.  Place  about  20  grams  of  soil  in  the  flask  and  add  a 
measured  quantity  of  distilled  water,  and  shake  well  to  expel  the 
air  from  the  soil. 

Fill  the  flask  up  to  the  mark  from  the  burette,  and  note  the 
total  amount  of  water  used,  including  the  hygroscopic  water  of  the 
soil.  This  amount,  subtracted  from  the  volume  of  the  flask,  will 
give  the  water  displaced  by  the  soil.  Calculate  the  specific  gravity 
and  tabulate  the  results. 

Use  for  this  experiment  sand,  clay,  and  loam  soils. 

VII.  —  Questions  concerning  the  Weight  of  Soils 

If  the  soil  were  a  solid  mass,  the  determination  of  its 
weight  would  be  a  simple  matter.  The  specific  gravity 
of  the  material  which  forms  the  great  bulk  of  most  soils 
is  about  2.6.  Since  a  cubic  foot  of  water  weighs 
nearly  62|-  pounds,  a  cubic  foot  of  soil,  then,  would 


STUDIES  ABOUT  SOILS  17 

weigh  2.6  times  62^  pounds,  or  162|  pounds.  (This,  of 
course,  refers  to  the  weight  of  water-free  soil.) 

But  the  fact  is,  a  soil  is  not  a  solid  mass.  On  the 
contrary,  it  is  composed  of  more  or  less  spherical  par- 
ticles which  touch  each  other  only  at  certain  points 
of  contact.  Nearly  50  per  cent  of  a  given  volume  of 
cultivated  soil  is  air  space.  This  pore  space  necessa- 
rily reduces  the  weight  of  any  volume  of  soil  much 
below  the  specific  gravity  of  its  constituents  ;  hence, 
we  use  the  two  terms,  "  real  specific  gravity  "  and  "  ap- 
parent specific  gravity." 

There  is  a  wide  variation  in  the  weights  of  different 
arable  soils,  owing  to  the  differences  in  the  amounts  of 
humus  in  their  composititDu,  and  in  the  size  of  their  soil 
particles.  For  these  reasons  surface  soils  are  usually 
lighter  than  subsoils.  A  fertile  garden  soil  weighs 
about  70  pounds  per  cubic  foot,  while  an  ordinary  sandy 
loam  weighs  90  to  95  pounds. 

The  figures  taken  for  the  approximate  weight  of  dry 
soil  on  an  acre  of  arable  land  are  4,000,000  pounds  to 
the  depth  of  12  inches,  and  2,000,000  pounds  for  the 
7  surface  inches. 

Exercises  7,  8,  9,  and  10  are  given  that  the  student 
may  have  opportunity  to  verify  the  statements  made 
by  different  writers  in  regard  to  the  weights  and 
specific  gravities  of  soils,  and  also  that  he  may  learn  at 
first  hand  how  soils  of  different  types  compare  in  these 
respects. 

References  :  Fletcher,  Soils,  pp.  26-27.  Snyder,  Soils  and  Fertil- 
izers, pp.  9-11.    Warington,  Physical  Properties  of  Soil,  pp.  41-49. 


18  MANUAL  OF  AGRICULTURE 

Vm.  —  Porosity  of  Soils 

As  has  been  stated  in  a  former  paragraph,  because 
the  soil  mass  is  made  up  of  rounded  particles  more  or 
less  loosely  packed  together,  there  is  left  between  them 
a  considerable  space  that  is  occupied  by  air  or  water, 
and  is  called  the  pore  space  of  the  soil.  The  amount 
of  pore  space  varies  from  something  over  50  per  cent  in 
very  fine  clay  soils  to  25  or  30  per  cent  in  coarse  sands 
of  uniform  texture.  It  is  greatest  in  the  fine-grained 
soils  because  these  particles,  unlike  those  of  sandy  soils, 
are  too  light  to  pack  closely  of  their  own  weight. 

Under  ordinary  field  conditions  of  a  cultivated  soil, 
the  pore  space  is  increased  by  the  stirring  of  the  ground 
and  the  addition  of  organic  matter.  It  is  the  pore 
space  of  a  soil  which  measures  its  capacity  to  hold 
water.  For  example,  if  50  per  cent  of  the  surface  foot 
of  a  certain  soil  is  pore  space,  the  capacity  of  that  soil 
to  take  up  water  before  it  is  forced  to  flow  away  over 
the  surface  or  to  penetrate  deeper  into  the  ground  is 
equal  to  six  inches  of  rainfall. 

Moreover,  the  various  forms  of  living  organisms  that 
work  in  the  soil  and  are  essential  to  its  fertility  require 
the  presence  of  air  to  live  and  work.  Both  the  oxygen 
and  the  nitrogen  in  the  air  are  needed  for  the  chemical 
combinations  that  take  place  in  a  fertile  soil.  The 
roots  of  growing  plants  demand  air  just  as  animals  do, 
and  when  the  supply  is  shut  off  the  plants  die. 

For  all  these  reasons  a  fertile  soil  must  have  a  gen- 
erous amount  of  pore  space  for  the  circulation  of  air. 


STUDIES  ABOUT  SOILS  19 

These  are  important  matters  in  the  business  of  grow- 
ing crops,  and  the  farmer  should  thoroughly  understand 
and  appreciate  them. 

Exercise  11  presents  two  methods  for  determining 
the  amount  of  pore  space  in  soils. 

Reference  :  Warington,  Physical  Properties  of  Soil,  pp.  64-73. 

Exercise  11 

Determinatioyi  of  Porosity 

First  Method 

Weigh  a  graduated  cylinder. 

Use  sand,  loam,  silt,  clay,  and  peat. 

Fill  to  the  50  or  100  cubic  centimeter  mark  with  soil  not 
compacted,  and  weigh.  Compute  the  amount  of  water-free  soil  in 
this. 

( Volume  of  soil  x  real  specific  gravity)  —  wt.  of  water-free  soil 
Volume  of  soil  x  reaZ  specific  gravity 

=  per  cent  of  pore  space. 
What  effect  does  size  of  particles  have  on  total  amount  of  pore 
space  1 

Does  the  amount  of  pore  space  increase  or  decrease  with  the 
amount  of  organic  matter  1 

Which  of  the  soils  have  the  largest  pores  ?  Does  this  mean  the 
greatest  amount  of  pore  space  ? 

Second  Method 

Find  what  per  cent  the  apparent  specific  gravity  is  of  the  real 
specific  gravity,  and  subtract  this  from  100  per  cent.  The  re- 
mainder expresses  the  per  cent  of  pore  space  in  the  soil. 


20  MANUAL  OF  AGRICULTURE 

Why  does  the  porosity  of  soils  vary  as  the  apparent  specific 
gravity  1 

IX.  —  The  Organic  Matter  in  Soils 

The  common  sources  of  the  organic  matter  in  soils 
are  plants  and  animals  whose  bodies,  after  life  leaves 
them,  fall  to  the  ground  and  are  gradually  disintegrated 
and  mingled  with  the  finely  ground  portions  of  the 
earth's  crust.  Here,  through  the  action  of  soil  bacteria, 
the  particles  are  decomposed  into  the  elements  from 
which  they  were  originally  formed,  and  thus  their  cycle 
of  existence  is  completed. 

In  the  intermediate  stages  of  decomposition  this 
organic  matter  in  the  soil  is  called  humus,  and  is  a  most 
important  factor  in  the  matter  of  the  soil's  producing 
power. 

Humus  is  the  chief  source  of  soil  nitrogen.  Its  pres- 
ence in  the  soil  usually  imparts  to  it  the  dark  color 
which  is  regarded  as  one  of  the  surest  indications  of 
a  fertile  soil.  Many  of  the  most  important  physical 
properties  essential  to  the  permanent  productiveness  of 
soils  are  dependent  upon  the  presence  of  a  certain  pro- 
portion of  organic  matter  mixed  with  the  rock  particles. 

In  Exercise  12  the  student  is  given  a  method  of  de- 
termining with  some  degree  of  accuracy  the  per  cent  of 
organic  matter  in  any  given  sample  of  soil.  Ignition 
is  not  regarded  as  an  altogether  satisfactory  means  of 
taking  this  measure,  because  the  heat  that  consumes 
the  organic  matter  also  drives  off  any  volatile  salts  and 
water  of  hydration  present,  thus  indicating  by  the  loss 


STUDIES  ABOUT  SOILS  21 

of  weight  in  the  ignited  soil  a  greater  amount  of  or- 
ganic matter  than  the  soil  may  have  contained.  This 
is  especially  true  in  the  case  of  clay  subsoils.  However, 
with  most  surface  soils  the  results  are  approximately 
correct  and  are  of  value  in  making  comparisons  between 
different  soils. 

References  :  King,  The  Soil,  pp.  94-95.     Eletcher,  Soils,  pp.  53, 
72,  322-333.     Snyder,  Soils  and  Fertilizers,  pp.  86-96. 


Exercise  12 

Determination  by  Ignition  of  the  Loss  of  Organic  Matter  by 

Cropping 

It  is  a  recognized  fact  that  constant  cropping  with  grain  tends 
to  diminish  rapidly  the  amount  of  organic  matter  in  the  soil  unless 
great  care  is  taken  to  maintain  the  supply  by  the  use  of  green 
manure  crops  or  the  application  of  farmyard  manure.  This  loss 
changes  the  physical  character  of  the  soil.  The  result  is  to  destroy 
granulation,  lessen  the  water-holding  capacity  of  the  soil,  lower 
the  temperature,  and  interfere  with  proper  aeration. 

Get  one  sample  of  the  surface  soil  from  a  field  that  has  been 
cropped  heavily  for  years,  and  another  sample  from  the  sod  border 
as  near  as  possible  to  this  field,  and  determine  the  loss  in  weight  of 
each  soil  on  ignition,  which  will  give  an  indication  of  the  organic 
matter  content. 

Weigh  out  5  grams  of  water-free  soil,  or  air-dry  soil  calculated 
to  a  water-free  basis,  and  ignite  in  a  small  crucible  to  low  red  heat 
for  15  to  20  minutes.     Cool  in  a  desiccator  and  weigh. 

Tabulate  your  results. 

Which  of  the  soils  loses  more  ?     Why  ? 


22  MANUAL  OF  AGRICULTURE 

X.  —  The  Water-retaining  Power  of  Soils 

The  capacity  of  a  soil  to  absorb  or  hold  water  is 
limited  by  the  amount  of  its  total  pore  space,  which,  as 
is  shown  in  previous  paragraphs,  varies  according  to  the 
composition  and  texture  of  the  soil  from  about  25  per 
cent  to  more  than  50  per  cent.  This  means  that  a  satu- 
rated soil  may  contain  from  436  tons  to  697  tons  of 
water  in  the  upper  foot  of  soil  on  an  acre. 

However,  a  productive  soil  is  never  saturated  with 
water  except  possibly  for  a  short  time  immediately 
after  a  long  and  heavy  rainfall.  Soils  in  which  water 
stands  for  any  length  of  time  filling  the  pore  spaces  are 
boggy  and  unproductive,  and  the  water-table  must  be 
lowered  by  artificial  drainage  before  the  lands  can  be 
valuable  for  farming  purposes. 

But  it  is  the  power  of  drained  soils  to  retain  moisture, 
which  is  of  real  interest  to  the  farmer,  for  this  is  the 
water  supply  on  which  the  growing  crops  must  depend. 

It  has  been  stated  in  a  former  paragraph  that  the 
moisture  which  is  retained  in  a  soil  is  held  there  in  the 
form  of  a  film  around  each  soil  particle,  and  is  known 
as  capillary  moisture.  Hence,  it  is  readily  seen  that 
the  soil  which  possesses  in  any  given  volume  the  great- 
est surface  area  in  the  grains  which  compose  it  has  the 
greatest  water-retaining  capacity.  For  this  reason  the 
finest-grained  soils  have  the  greatest  power  to  retain 
moisture.  This  is  illustrated  as  follows:  In  a  cubical 
box  measuring  12  inches,  only  one  ball  having  a  diame- 
ter of  12  inches  can  be  placed.     The  surface  of  this 


STUDIES  ABOUT  SOILS  23 

ball,  by  the  formula  for  finding  the  surface  of  a  sphere 
(^S  =  IT  D  ^),  equals  144  tt  inches.  If  balls  of  half  this 
diameter  be  placed  in  the  box,  it  will  contain  eight  of 
them,  and  their  combined  surfaces  (>S'=7rx6x6x8) 
are  288  tt  inches.  That  is,  by  reducing  the  diameters  of 
the  spheres  by  one  half,  the  aggregate  area  of  their  sur- 
faces is  doubled. 

While  the  soil  particles  composing  any  soil  are  not 
perfect  spheres  and  are  not  of  uniform  size,  it  still  holds 
that  the  finer  the  grains  and  the  greater  the  number  of 
them  in  a  given  volume  of  soil  the  greater  will  be  the 
internal  surface  of  the  soil  and  the  greater  its  water- 
retaining  power. 

Exercise  13,  therefore,  is  a  practical  demonstration 
of  the  differences  in  the  capacities  of  soils  to  retain 
moisture  largely  in  accordance  with  the  relative  sizes  of 
their  soil  particles. 

References  :  King,  The  Soil^  pp.  157-162.  Fletcher,  Soils^ 
pp.  80-82.     Warington,  Physical  Properties  of  Soil,  pp.  74-85. 

Exercise   13 

Power  of  Soils  to  retain  Water 

Fill  tubes  having  perforated  bottoms  with  sand,  silt,  loam,  and 
clay. 

Before  filling,  place  disks  of  damp  cheese  cloth  in  the  bottoms  of 
the  tubes  and  then  weigh  them.  FUl  the  tubes  up  to  the  crease, 
one  inch  from  the  top,  by  pouring  the  soil  in  gently  through  a  fun- 
nel, the  tube  being  held  vertically,  and  be  careful  not  to  compact  the 
soil  by  jarring.     Weigh  the  filled  tubes  and  place  in  an  empty  gal- 


24  MANUAL   OF  AGRICULTURE 

vanized  iron  box.  Pour  water  into  the  box  till  it  is  on  the  same 
level  with  the  soil  in  the  tubes,  thus  allowing  the  water  to  pass  up 
through  the  soils.  Note  time  required  for  soils  to  become  moist  on 
top.  When  the  soils  have  become  thoroughly  saturated,  remove 
the  tubes  and  place  them  in  a  pan  to  drain.  Weigh  from  day  to 
day  till  drainage  ceases. 

Determine  the  amount  of  water-free  soil  by  finding  total  mois- 
ture content  of  the  soil  when  used. 

Measure  depth  of  the  settled  soils. 

Calculate  the  per  cent  of  water  retained,  the  weight  per  cubic 
foot  of  soil  that  this  represents,  using  the  apparent  specific  gravity 
and  the  acre  inches  of  water. 

Express  your  results  in  tabular  form. 

Land  recently  plowed  six  inches  deep  will  absorb  how  many 
inches  of  rainfall  without  any  run-off? 

Is  there  any  advantage  in  deep  plowing  on  rolling  land  ? 

What  is  a  saturated  soil  ? 


XI.  —  Effect  of  compacting  the  Soil 

There  is  some  difference  of  opinion  among  farmers 
as  to  whether  rolling  or  otherwise  compacting  the  soil 
increases  its  capacity  to  retain  moisture.  It  is  fre- 
quently apparent  that  the  soil  on  the  surface  of  the 
ground  where  it  has  been  packed  by  footprints  has 
more  moisture  than  the  loose  soil  around  it.  It  is  true 
that,  by  pressing  more  closely  together  the  grains  of 
loose  material  on  the  surface  and  destroying  the  open 
spaces  which  were  too  large  to  exert  capillary  action, 
the  movement  of  water  from  below  towards  the  surface 
has  been  increased,  and  for  a  time  there  will  be  a  gain 


STUDIES   ABOUT  SOILS  25 

in  the  amount  of  water  in  the  upper  layer  of  the  soil, 
but  at  the  expense  of  the  layers  below.  In  the  case  of 
some  very  light  soils,  where  the  particles  in  their  com- 
position are  quite  uniformly  coarse  and  the  pore  spaces 
large,  compacting  undoubtedly  increases  their  water- 
retaining  power. 

Exercise  14  is  given  for  the  purpose  of  comparing 
compact  soils  with  loose  soils  to  determine  which  has 
the  greater  capacity  to  retain  water. 

References  :  King,  The  Soil,  pp.  200-202.  Fletcher,  Soils,  pp. 
171-177. 

Exercise  14 

Power  of  Compact  Soils  to  retain   Water 

Use  the  same  tubes  and  soils  as  in  Exercise  13,  and  run  them  at 
the  same  time  if  possible.  When  you  have  filled  the  tubes  one- 
third  full  of  soil,  hold  them  vertically  six  inches  above  a  solid  table, 
and  let  them  fall  three  times  ;  repeat  this  when  two-thirds  full,  and 
again  when  full.  Use  great  care  to  compact  the  soil  in  all  the  tubes 
alike.  ^ 

Conduct  the  experiment  precisely  as  in  the  previous  exercise, 
except  in  compacting  the  soils.  Calculate  the  per  cent  of  water 
retained,  the  weight  of  water  per  cubic  foot  of  soil,  using  the  ap- 
parent specific  gravity  and  the  acre  inches  of  water  for  each  soil. 

Tabulate  your  results. 

1  In  the  soil-physics  laboratories  of  agricultural  colleges  an  appara- 
tus for  compacting  the  soils  uniformly  is  used.  An  iron  plunger  just 
fitting  the  soil  tubes  is  attached  to  the  end  of  a  rod  on  which  moves 
freely  a  weight  of  several  pounds.  The  plunger  is  placed  upon  the  soil 
in  the  tube  and  the  weight  dropped  a  given  number  of  times  from  a 
mark  on  the  rod.     A  strong  wood  frame  is  needed  for  the  apparatus. 


26  MANUAL   OF  AGRICULTURE 

Which  soil  becomes  wet  on  top  first  ?  Why  ?  How  does  this 
coiTespond  with  total  pore  space?  Which  soil  is  drained  first? 
Why  ?  How  does  this  correspond  with  total  pore  space  ?  What 
effect  does  organic  matter  have  on  retention  of  water  ? 

How  does  rolling  affect  the  water-retaining  capacity  of  a  soil  ? 

« 

XII.  —  How  Organic  Matter  in  Soils  affects  their 

Water-holding  Power 

The  chief  object  sought  in  the  study  of  the  science 
of  agriculture  is  to  discover  how  the  farmer  may  con- 
trol or  modify  to  his  advantage  the  conditions  that 
affect  the  growing  of  crops.  It  is  certain  that  crop 
yields  are  often  seriously  limited  because  the  soil  does 
not  contain  sufficient  moisture  to  supply  their  needs. 

Exercise  15  is  given  that  the  student  may  test  the 
effect  of  an  increase  in  the  amount  of  organic  matter  in 
the  soil  upon  its  water-retaining  powers. 

References  :  King,  The  Soil,  pp.  288-291.  Snyder,  Soils  and 
Fertilizers,  pp.  37-38. 

Exercise  15 

Effect  of  Organic  Matter  on  Retention  of  Water 

Use  same  tubes  as  in  preceding  exercises,  but  compact  in  one, 
sand,  and  in  the  others,  sand  and  peat  in  the  following  propor- 
tions :  190  grams  of  sand  and  10  grams  of  peat  thoroughly  mixed  ; 
175  grams  of  sand  and  25  grams  of  peat ;  and  150  grams  of  sand 
and  50  grams  of  peat.^ 

1  If  peat  cannot  be  obtained  conveniently,  thoroughly  rotted  dry 
manure  may  be  used  in  its  place.  The  manure  should  be  made  fine 
by  rubbing  before  it  is  mixed  with  the  sand. 


STUDIES  ABOUT  SOILS  27 

Treat  as  in  the  preceding,  and  determine  the  grams  of  water  re- 
tained, also  the  per  cent  of  water  retained,  based  upon  the  total 
amount  of  sand  and  peat  used  in  each  tube. 

Tabulate  results. 

What  per  cent  of  organic  matter  was  in  each  tube  ? 

How  many  grams  of  water  did  the  10  grams  of  organic  matter 
retain  ?     The  25  grams  ?     The  50  grams  ? 

XIII.  —  Capillary  Movement  of  Soil  Moisture 

As  the  films  of  moisture  surrounding  the  soil  grains 
which  lie  near  the  surface  of  the  ground  are  removed 
by  evaporation  into  the  air,  and  others  enfolding  the 
particles  of  soil  at  greater  depths  are  taken  up  by  the 
tiny  root  hairs  to  supply,  the  plants  with  water,  there  is 
a  steady  flow  of  moisture  from  below  and  from  every 
side,  if  the  soil  is  in  a  proper  state  of  tilth,  to  take  the 
place  of  that  which  has  been  withdrawn.  This  move- 
ment of  moisture  through  the  ground  is  made  possible 
by  the  capillary  action  of  soils,  and  in  some  soils  its 
force  is  exerted  through  distances  of  many  feet.  If  it 
were  not  for  this  capillary  movement  of  moisture  in 
soils,  it  would  be  utterly  impossible  in  many  regions  to 
grow  crops,  since  there  is  no  rainfall  there  during  the 
growing  season.  Indeed,  there  are  few  places  where 
the  rainfall  is  sufficient  in  quantity  and  distributed 
evenly  enough  during  the  months  in  which  crops  make 
their  growth  to  meet  their  needs  for  moisture  if  none 
could  be  pumped  up  from  the  reservoirs  below. 

This  power  of  a  soil  to  move  water  through  its  mass 
is  so  largely  dependent  upon  physical  conditions  which 


28  MANUAL  OF  AGRICULTURE 

cultivation  can  affect  that  it  should  be  one  of  the  sub- 
jects of  greatest  interest  and  study  for  the  farmer. 

In  Exercise  16  the  students  are  able  to  observe  the 
relative  lifting  powers  of  soils  of  different  types  and 
of  soils  of  the  same  type  but  in  different  conditions  of 
-tilth. 

The  value  of  such  ocular  demonstrations  to  a  student 
of  the  processes  which  are  constantly  in  operation  in 
the  soil  under  his  feet,  and  which  it  is  possible  for  him 
to  control,  in  a  large  measure,  to  the  advantage  of  his 
crops,  if  he  understands  the  principles  on  which  these 
processes  work,  makes  exercises  of  this  sort  especially 
desirable. 

References  :  King,  The  Soil,  pp.  135-142.  Fletcher,  Soils,  pp. 
87-90,  95-96.     Warington,  Physical  Properties  of  Soil,  pp.  92-108. 


Exercise  16 

A  Study  of  the  Capillary  Action  of  Soils 

The  capillary  power  of  soils  is  influenced  by  several  factors,  the 
most  important  of  these  being  the  physical  composition,  texture, 
and  compactness  of  the  soil.  In  field  soils  all  these  are  changed 
by  continuous  cropping,  and  the  capillary  action  is  therefore  al- 
tered. Of  these  factors,  physical  composition  is  most  important, 
especially  the  amount  of  the  diff'erent  grades  of  the  inorganic 
constituents. 

The  soils  selected  are  as  follows  :  — 

1.  Fine  sand. 

2.  Coarse  sand. 

3.  Loam. 


STUDIES  ABOUT  SOILS  29 

4.  Clay. 

5.  Sod  from  an  old  pasture. 

6.  Heavily  cropped  soil  as  near  the  type  of  5  as  possible. 

Use  glass  tubes  one  inch  in  diameter  and  four  or  five  feet  in 
length.  One  end  of  the  large  glass  tubes  is  closed  by  means  of  a 
piece  of  muslin  firmly  tied  on.  These  tubes  are  then  filled  with 
the  finely  pulverized  and  sifted  air-dried  soils.  Great  care  must- 
be  exercised  in  filling  these  tubes  so  as  not  to  separate  the  coarse 
and  fine  particles.  This  may  best  be  accomplished  by  holding 
the  tube  vertically  during  the  process  of  filling.  When  the  tubes 
are  filled,  the  soil  is  compacted  slightly  by  letting  each  tube  drop 
four  times  a  distance  of  four  inches  upon  a  book.  The  tubes  are 
now  placed  in  a  suj)porting  frame  in  such  a  manner  that  the  ends 
shall  dip  one-half  inch  beneath  the  surface  of  the  water  contained 
in  the  tray.^  The  experiment  is  now  ready  for  observation,  and  the 
datum  to  be  obtained  at  each  reading  is  the  total  height  to  which 
the  water  has  risen.  The  readings  are  to  be  taken  as  nearly  as 
possible  at  the  intervals  stated  below  and  tabulated. 

Observe  height  of  moisture  after  -J-  hour,  1  hour,  2  hours,  3 
hours,  6  hours,  9  hours,  12  hours,  24  hours,  36  hours,  48  hours; 
3,  4,  5,  6,  7,  and  8  days. 

Make  a  close  comparison  of  the  diff'erent  tubes. 

Which  shows  the  most  rapid  rise  1     Why  ? 

Plot  the  heights  of  the  water  of  the  different  tubes  at  different 
times. 

At  the  end  of  one  hour,  which  shows  the  greatest  rise,  clay  or 
sand  ?     Which  at  the  end  of  a  week  1     Why  ? 

What  effect  does  organic  matter  have,  as  shown  in  5  and  6  1 

What  effect  does  size  of  particles  have  on  rapidity  of  capillary 
movement,  not  taking  height  into  account  ? 

1  Arrange  so  that  there  shall  be  a  continuous  flow  of  water  through 
the  tray,  keeping  the  depth  half  an  inch  above  the  bottoms  of  the  tubes. 


30  MANUAL   OF  AGRICULTURE 

XIV.  —  A  Common  Mistake  in  applying  Manure 

Exercise  17  differs  from  No.  16  only  in  providing  for 
experiments  to  determine  the  effect  on  the  capillary 
movement  of  water  caused  by  the  application  of  farm 
manures  or  the  plowing  under  of  green  crops. 

The  tests  may  easily  be  varied  from  time  to  time  to 
cover  a  great  many  different  conditions  and  to  answer 
questions  that  may  arise  in  the  minds  of  the  students 
as  to  what  would  be  the  results  of  certain  practices. 

If  the  crop  at  any  time  during  its  growing  season  is 
forced  to  depend  for  its  moisture  upon  the  supply  of 
water  which  is  held  in  store  at  some  distance  below  the 
surface,  any  material,  like  coarse  manure  or  unrotted 
clover,  which  breaks  the  connection  of  capillary  tubes 
in  the  soil  between  the  stratum  where  the  plant  roots 
are  growing  and  the  one  in  which  the  water  is  held 
will  prove  to  be  a  serious  disadvantage  to  the  crop. 

Experiments  like  the  following  are  especially  valuable, 
because  they  make  clear  to  the  student  the  reasons  why 
certain  ways  of  doing  things  on  the  farm  frequently 
give  bad  results. 

Exercise  17 

Effect  of  Organic  Matter  on  Rise  of  Water  in  Soils 

Class  exercise  in  which  each  member  of  the  class  is  to  take 
daily  observations  on  the  height  of  the  water  in  the  tubes  and 
note  effect  of  organic  matter  on  rise  of  water. 

After  tying  a  cloth  firmly  over  the  ends  of  three  two-inch  glass 
tubes  two  feet  long,  fill  them  to  the  height  of  one  foot  with  soil 


STUDIES  ABOUT  SOILS  31 

compacted  by  letting  the  tube  drop  four  times  on  a  book  from 
height  of  four  inches  for  every  six  inches  of  soil  put  into  the  tube. 

Use  finely  pulverized,  air-dried  loam,  filling  tube  No.  1  with  the 
soil  alone.  Fill  tube  No.  2  with  one  foot  of  soil,  then  add  a  two- 
inch  layer  of  cut  straw  or  sawdust,  and  fill  to  the  top  with  soil. 
Fill  the  third  tube  in  the  same  way,  except  that  a  one-inch  layer 
of  fine,  well-rotted  manure  is  used  in  place  of  the  straw  or  sawdust. 

Place  the  tubes  in  a  frame  so  that  the  lower  ends  shall  stand  in 
half  an  inch  of  water.  Notice  the  rise  of  capillary  water  in  each 
tube,  and  at  the  end  of  a  week  make  a  complete  report  of  your 
observations. 

What  is  the  effect  of  plowing  under  large  amounts  of  poorly 
rotted  manure  in  the  spring  ? 

What  advantage  in  this  respect  has  fall  plowing  ? 

XV.  — The  Farmer's  Control  of  Soil  Moisture 

The  control  of  the  moisture  relations  of  soils  in- 
cludes :  — 

1.  Increasing  the  amount  of  water  in  the  soil  either 
by  irrigation  or  by  rendering  the  surface  more  loose  and 
porous,  so  that  it  will  absorb  a  larger  proportion  of  the 
water  that  falls  upon  it  in  the  shape  of  rain  and  melt- 
ing snows. 

2.  Diminishing  the  amount  of  water  in  the  soil  either 
by  conducting  it  away  through  surface  ditches  before 
it  soaks  into  the  ground,  or  by  tile  drains  laid  beneath 
the  surface  for  the  purpose  of  lowering  the  water- 
table. 

3.  Increasing  the  water-holding  capacity  of  the  soil 
by  cultivation  and  the  application  of  organic  matters. 


32  MANUAL  OF  AGRICULTURE 

4.  Hastening  or  retarding  the  movements  of  water 
in  the  soil  by  different  kinds  of  cultivation,  or  by  the 
use  of  manures  and  green  crops  plowed  under. 

5.  Conserving  the  supply  of  water  that  has  already 
been  taken  into  the  soil,  and  preventing  its  unnecessary 
loss  by  evaporation  from  the  surface. 

All  these  questions  except  the  last  have  been  dis- 
cussed in  previous  exercises.  In  Exercise  18  the  object 
is  to  discover  the  most  effective  and  satisfactory  methods 
of  conserving  soil  moisture  by  means  of  tillage. 

In  the  study  of  the  capillary  movements  of  water  it 
was  seen  that  large  amounts  of  moisture  in  many  soils 
were  being  moved  continuously  from  lower  strata  of 
soil  to  the  upper  zone  to  replace  that  which  was  being 
carried  away  in  the  atmosphere  by  evaporation.  The 
water  so  removed  is  thus  of  no  value  to  the  crop,  and  is 
usually  a  serious  loss.  By  destroying  the  capillary 
tubes  that  have  formed  close  to  the  surface,  the  upward 
flow  of  moisture  can  be  checked  at  this  point  and  much 
loss  of  water  be  prevented.  Frequent  surface  cultiva- 
tion, for  this  reason,  has  been  shown  to  be  very  effective 
in  promoting  the  growth  of  crops  in  semiarid  sections 
of  the  country  and  in  all  sections  during  protracted  dry 
spells.  The  shallow  stirring  of  the  earth  breaks  up  the 
capillary  tubes  that  have  formed  in  the  compacted  sur- 
face and  spreads  a  loose  blanket  of  dry  earth  —  a  dust 
mulch  —  over  the  surface. 

Now  in  connection  with  this  there  are  some  questions 
that  the  farmer  needs  to  have  answered,  such  as  :  What 
depth  of  cultivation  shows  the  best  results  in  the  con- 


STUDIES  ABOUT  SOILS  33 

servation  of  moisture  ?     How  frequently  should  this  cul- 
tivation be  repeated  to  be  most  effective  ? 

References:    King,     The    Soil,    pp.    184-190.     Fletcher,    Soils, 
pp.  90-92,  107-110.     Snyder,  Soils  and  Fertilizers,  p.  27. 


Exercise  18 

Effect  of  Soil  Middies  on  Evaporation  of  Watei-  from  Soils 

Fill  all  the  tubes,  with  the  same  kind  of  soil,  compacting  each  ^ 
three  inches,  and  pouring  enough  water  upon  it  to  make  it  thor- 
oughly moist.  Fill  to  within  a  half  inch  of  the  top,  but  do  not 
pour  water  on  the  top.  The  enlarged  bases  of  the  tubes  are  then 
partially  fQled  with  water,  and  the  tubes  are  left  till  the  surface 
soil  becomes  moist.  The  tubes  are  then  ready  for  use.  As  the 
water  evaporates  from  the  surface  it  must  be  replaced  from  day 
to  day  by  refilling  the  base,  the  exact  weight  of  wgter  added  in 
each  case  being  noted. 

The  loss  of  water  is  determined  by  the  loss  in  weight  of  the 
tubes.     Weigh  each  day. 

Tube  1,  check  (no  cultivation).^ 

1  The  tubes  used  for  this  experiment  are  made  of  light  galvanized 
iron,  and  are  18  inches  long  and  6  inches  in  diameter.  The  bases  are 
3  inches  high  and  8  inches  in  diameter.  There  is  a  rim  round  the  top 
of  the  base,  leaving  an  opening  slightly  larger  than  the  tube.  A  col- 
lar is  soldered  around  the  tube  2f  inches  from  one  end,  so  that  the 
tube,  when  standing  in  its  base,  rests  on  the  collar,  leaving  ^-inch  space 
between  the  end  of  the  tube  and  the  bottom  of  the  base.  A  small 
tube,  closed  with  a  cork,  is  soldered  to  the  rim  of  the  base,  through 
which  water  can  be  supplied  as  needed. 

2  Cultivate  the  soil  each  morning  with  a  knife  to  the  depth  indicated, 
being  careful  to  lose  none  in  the  operation,  as  this  would  destroy  the 
accuracy  of  the  weights  taken. 


34  MANUAL  OF  AGRICULTURE 

Tube  2,  cultivated  1  inch  deep. 

Tube  3,  cultivated  2  inches  deep. 

Tube  4,  cultivated  3  inches  deep. 

Tube  5,  cultivated  4  inches  deep. 

The  cultivations  should  be  made  every  day  to  the  required  depth. 
Each  tube  has  an  area  of  ^  2  i"^8  5  o  ^^  ^^  acre,  and  the  results  are  to 
be  computed  in  tons  of  water  evaporated  per  acre  per  week.  It  is 
very  necessary  that  the  tubes  all  have  the  same  exposure  to  heat 
and  air  currents. 

Upon  what  principle  does  a  soil  mulch  conserve  moisture  ? 

What  efiect  will  cultivation  have  on  a  very  wet  soil  ? 

If  the  water-table  were  12  inches  from  the  surface  instead  of 
24,  what  difference  would  there  be  in  your  results  ? 

Is  there  any  argument  in  the  experiment  in  favor  of  fall  plowing  ? 

Does  it  show  the  value  of  cultivating  as  soon  as  possible  after  a 
heavy  rain  ? 

XVI.  —  Mulches  of  Various  Materials 

For  field  crops  of  large  areas  the  dust  mulcli  secured 
by  surface  cultivation  is  probably  the  most  practicable 
method  of  conserving  soil  moisture ;  but  on  more  re- 
stricted areas  devoted  to  orchards,  small  fruits,  and 
gardens,  it  is  possible  to  employ  artificial  mulches  of 
manure,  straw,  leaves,  clippings  from  the  lawn,  saw- 
dust, peat,  or  sand.  There  are  sometimes  other  ad- 
vantages than  the  conservation  of  moisture  secured  in 
the  use  of  these  mulches ;  for  instance,  in  the  growing 
of  some  vegetables,  such  as  potatoes,  the  protection  of 
the  roots  and  tubers  from  too  intense  heat  seems  to  give 
good  results.     However,  in  Exercise  19  the  thing  to 


STUDIES   ABOUT   SOILS  35 

be  determined  is  the  relative  effectiveness  of  artificial 
mulches  of  different  materials. 

References  :  Fletcher,  Soils,  pp.  90-91.  Snyder,  Soils  and  Fer- 
tilizers, p.  35. 

Exercise  19 

Effect  of  Artijicial  Mulches  uj^on  Evaporcition  of  Water 

from  Soils 

Fill  tubes,  as  in  preceding  exercise,  to  within  one  inch  of  top,  and 
then  fill  the  remaining  part  with  material  for  mulch.  Proceed  as 
in  Exercise  18. 

Tube  1,  check  (filled  to  top  with  same  kind  of  soil). 

Tube  2,  one  inch  of  sand. 

Tube  3,  one  inch  of  gravel. 

Tube  4,  one  inch  of  peat. 

Tube  5,  one  inch  of  sawdust  or  cut  straw. 

The  area  of  each  tube  is  221850  ^^^®- 

Compute  loss  of  water  in  tons  per  acre  per  week  and  tabulate 
results. 

What  will  be  the  eS'ect  of  these  mulches  on  temperature  ? 

What  is  the  principle  of  the  growing  of  "straw  potatoes,"  i.e. 
covered  with  straw  and  not  cultivated  ? 

XVII.  —  Improvement  of  Heavy  Soils  by  Use  of  Farm 

Manure 

We  speak  of  clays  as  heavy  soils  and  sands  as  light 
soils,  meaning  not  the  relative  weights  of  these  soils, 
which  is  just  the  reverse  of  what  the  terms  indicate, 
but  that  clays  are  plastic  and  sticky  and  difficult  to 


86  MANUAL  OF  AGRICULTURE 

handle  when  moist,  while  sands  are  loose  and  crumbly 
even  when  wet. 

This  characteristic  of  clay  makes  it  a  difficult  and 
often  unpleasant  soil  to  cultivate,  since  one  must  ex- 
ercise great  care  and  judgment  in  not  tilling  it  when  it 
is  too  wet,  and  if  it  becomes  too  dry  before  working,  it 
bakes  so  solidly  that  it  can  only  be  broken  up  into 
lumps;  so  that  often  no  amount  of  labor  can  get  the  soil 
into  good  condition  for  cropping  that  season. 

This  undesirable  quality  in  clays  is  due  to  the  fine- 
ness of  their  particles,  which  allows  them  to  pack  too 
closely  together.  As  was  demonstrated  in  Exercise  6, 
the  application  of  lime  to  such  soils  causes  the  fine 
particles  to  flocculate  and  form  larger  crumbs  of  material, 
which  gives  a  looseness  to  the  soil  and  helps  to  modify 
its  plasticity. 

Another  way  to  treat  clay  soils  to  make  them  lighter 
and  more  porous  in  texture  is  to  mix  with  the  soil  a 
dressing  of  manure,  leaf  mold,  or  some  other  form  of 
organic  matter. 

The  work  in  Exercise  20  is  to  demonstrate  the  bene- 
ficial effects  of  working  organic  matter  into  heavy  clay 
soils,  and  to  get  some  idea  of  the  approximate  amounts 
that  should  be  used  in  order  to  change  materially  their 
character. 

References  :  Fletcher,  Soils^  pp.  322-327.  Snyder,  Soils  and 
Fertilizers^  pp.  93-96. 


STUDIES  ABOUT  SOILS  37 

Exercise  20 

TJie  Effect  of  Organic  Matter  on  Baking  of  Clay  Soils 

Use  four  one-gallon  earthen  jars  provided  with  drainage  outlets, 
and  fill  them  to  within  one  inch  of  the  top  as  follows  :  — 

No.  1.     Clay. 

No.  2.  Clay  thoroughly  mixed  with  5  per  cent  of  peat  by 
weight.     (Fine,  dry,  well-rotted  manure  may  be  used.) 

No.  3.  Clay  thoroughly  mixed  with  10  per  cent  of  peat  or 
manure  by  weight. 

No.  4.  Clay  thoroughly  mixed  with  20  per  cent  of  peat  or 
manure  by  weight.  Apply  enough  water  to  saturate  the  soil,  using 
the  same  amount  in  each  jar,  and  expose  all  the  jars  to  the  direct 
rays  of  the  sun  until  the  soil  is  baked. 

Test  the  soils  in  the  four  jars  to  compare  the  ease  with  which 
the  crust  can  be  pulverized  with  the  fingers. 

Write  out  fully  the  results  of  this  exercise. 

What  causes  a  clay  soil  to  bake  ? 

In  what  way  does  the  crust  thus  formed  injure  growing  plants  1 
How  can  a  farmer  prevent  the  baking  of  his  soil  ? 


PART   II. —STUDIES   ABOUT   CROPS 

XVm.  — What  Foods  Plants  Use  and  How  They 

are  Obtained 

In  the  first  twenty  exercises  of  the  Manual  the  study 
and  experiments  have  had  for  their  object  a  better 
understanding  of  the  physical  properties  of  the  soil  in 
its  environmental  relations  to  the  plant. 

The  soil  is  called  the  home  of  the  plant,  inasmuch  as 
it  is  its  natural  abiding  place  throughout  its  life,  furnish- 
ing a  spot  for  the  anchorage  of  its  roots,  where  they 
may  find  congenial  surroundings  as  regards  moisture, 
heat,  and  air,  and  a  firm  support  from  which  to  lift  their 
aerial  parts  and  expose  the  leaf  surfaces  to  the  air. 

It  is  the  business  of  the  farmer  to  know  what  are  the 
needs  of  the  plant  in  these  respects,  and  then  how  to 
manage  his  soil  to  secure  in  the  fullest  degree  possible 
the  conditions  required. 

But  the  important  work  of  the  plant  is  to  grow  —  to 
take  into  its  tissues  certain  substances  that  lie  outside 
it,  to  transform  these  into  its  own  substance,  and  to 
build  them  up  into  its  various  parts,  thus  enlarging  and 
developing  itself  to  its  perfect  stature  and  the  comple- 
tion of  its  life's  functions. 

What,  then,  are  these  substances  which  the  plant  uses 
for  its  building  materials,  and  from  what  sources  does 

39 


40  MANUAL  OF  AGRICULTURE 

it  obtain  them  ?  These  questions  open  up  a  new  and 
broad  field  for  the  farmer's  investigation. 

Briefly  stated,  these  are  the  answers  that  are  now 
generally  accepted  for  the  above  question:  — 

1.  There  are  but  ten  elements  which  the  plant  re- 
quires for  complete  development  of  all  its  parts.  These 
are  carbon,  oxygen,  hydrogen,  nitrogen,  phosphorus, 
potassium,  calcium,  sulphur,  magnesium,  and  iron.  The 
symbols  used  to  represent  these  elements,  in  the  order 
in  which  they  have  been  named,  are  C,  O,  H,  N,  P,  K, 
Ca,  S,  Mg,  and  Fe. 

There  are  two  ways  of  determining  the  substances 
which  plants  require  for  the  building  of  their  parts. 
One  way  is  to  analyze  the  plants  and  so  learn  of  what 
materials  they  have  been  made.  In  all  plants  analyses 
always  show  the  presence  of  the  ten  elements  that  have 
been  named.  Usually  a  few  other  elements  —  silicon, 
chlorine,  and  sodium  most  frequently  —  are  found  pres- 
ent in  the  composition  of  the  plants. 

The  second  way  is  by  synthesis  —  to  grow  plants 
either  in  distilled  water  or  in  pure  sand,  which  insures 
that  the  growing  plants  get  no  plant  food  except  what 
the  grower  gives  to  them  and  what  they  secure  from 
the  air.  By  this  method  it  is  demonstrated  beyond  all 
doubt  that  no  plant  can  attain  perfect  development  if 
not  supplied  with  all  of  the  ten  elements,  C,  O,  H,  N, 
P,  K,  Ca,  S,  Mg,  and  Fe,  and  that  the  omission  of  any 
or  all  other  substances  in  no  way  retards  growth. 

Moreover,  in  answer  to  the  second  question,  as  to  the 
sources  from  which  plants  get  their  supplies  of  these 


STUDIES  ABOUT  CROPS  41 

essential  foods,  the  investigations  of  scientists  have 
shown  that  all  the  carbon  and  part  of  the  oxygen  used 
by  the  plant  are  taken  from  the  air  as  the  gaseous  com- 
pound, carhon  dioxide  (CO 2),  which  enters  the  plant 
through  minute  openings  in  its  leaves  called  stomata. 
The  hydrogen  and  the  remainder  of  the  oxygen  which 
the  plant  takes  up  are  secured  from  the  soil  in  the  form 
of  water,  which  is  a  compound  of  these  two  elements 
(HgO).  All  substances  which  plants  take  up  as  foods 
—  with  the  one  exception,  carbon  dioxide —  come  from 
the  soil  and  enter  the  plants  through  their  roots  in 
liquid  form.  That  is,  the  hydrogen  and  oxygen  are 
the  elements  of  which  the  water  is  composed,  and  the 
nitrogen,  phosphorus,  potassium,  calcium,  sulphur,  mag- 
nesium, and  iron  must  all  exist  in  the  soil  as  soluble 
compounds,  —  solids  like  salt  and  sugar  that  dissolve 
more  or  less  readily  in  the  water  in  the  soil,  —  and  so 
the  plants  obtain  them  in  solutions  with  the  water 
absorbed  by  their  roots. 

This  statement  again  emphasizes  the  lesson  of  so 
many  previous  exercises  —  the  immense  importance  of 
an  abundant  supply  of  water  for  the  crops,  since  water 
not  only  contains  two  of  the  essential  plant  foods,  but 
is  also  the  solvent  and  carrier  of  seven  of  the  other 
eight.  Six  of  these  seven  elements  —  phosphorus,  po- 
tassium, calcium,  sulphur,  magnesium,  and  iron — are 
mineral  compounds,  locked  up  in  the  soil  as  constitu- 
ents of  the  rocks.  Nitrogen,  however,  is  never  found 
as  an  element  in  the  composition  of  any  of  the  rocks  ; 
its  source  as  plant  food  in  the  soil  exists  in  the  various 


42  MANUAL  OF  AGRICULTURE 

organic  compounds  obtained  from  decaying  animal  and 
plant  tissues  —  the  humus  of  the  soil. 

Since  nearly  four  fifths  of  the  atmosphere  is  free 
nitrogen,  it  was  first  thought  that  plants  secured  their 
nitrogen,  as  they  do  their  carbon,  directly  from  the  air. 
But  this  was  long  ago  disproved,  though  the  belief 
continued  that  the  ultimate  source  of  nitrogen  in  all 
organic  compounds  was  the  limitless  supply  of  it  in  the 
air.  This  is  now  known  to  be  true,  and  the  claim  has 
been  made  that  no  other  discovery  in  the  science  of 
agriculture  promises  to  yield  results  of  such  importance 
to  the  farmers  as  this  :  that  there  are  certain  forms  of 
soil  bacteria  which  have  the  power  to  take  the  free 
nitrogen  directly  from  the  air  and  build  it  into  com- 
pounds that  the  plants  can  use. 

Moreover,  it  has  been  discovered  that  these  minute 
organisms  make  their  homes  and  perform  this  work  only 
on  the  roots  of  a  certain  kind  of  plants  called  legumes, 
which  are  best  represented  among  our  crops  by  the 
garden  and  field  peas  and  beans,  cowpeas,  soy  beans, 
the  various  kinds  of  clover  and  alfalfa.  For  each  vari- 
ety of  leguminous  plant  there  is  a  separate  variety  of 
bacteria  which  will  live  on  the  roots  of  this  particular 
legume  and  on  no  other.  (The  one  known  exception 
to  this  statement  is  found  in  the  case  of  the  germs  that 
live  on  the  roots  of  alfalfa.  These  also  thrive  on  sweet 
clover,  which  has  been  generally  regarded  as  a  weed.) 

The  presence  of  these  bacteria  in  a  soil  is  indicated 
by  the  little  tubercles  that  grow  on  the  roots  of  the 
legume  that  serves  as  the  host  plant  for  these  organ- 


STUDIES  ABOUT   CROPS  43 

isms.  These  tubercles  are  the  homes  of  colonies  of 
the  bacteria  —  millions  of  them  in  a  single  tubercle. 
The  bacteria  are  thought  to  live  on  the  juices  of  the 
plant's  roots,  and  in  return  they  furnish  the  plant  with 
the  nitrogen  which  they  have  the  power  to  take  from 
the  air  that  permeates  the  soil  about  the  roots  of  the 
plant.  In  this  way  the  plant  is  not  dependent  for  its 
nitrogen  upon  the  supply  in  the  soil,  and  when  the  crop 
is  plowed  under,  or  fed,  and  the  manure  returned  to  the 
field,  an  addition  of  this  essential  and  expensive  plant 
food  is  made  to  the  soil  without  extra  cost  to  the  farmer. 
Exercise  21  is  the  first  of  a  number  of  exercises  given 
in  the  Manual  to  teach  some  of  the  principles  of  soil 
fertility.     The  objects  of  this  exercise  are  :  — 

(1)  To  show  that  nitrogen,  phosphorus,  and  potas- 
sium are  essential  plant  foods,  and  if  the  plant  is  de- 
prived of  any  one  of  them  it  cannot  complete  its 
growth. 

(2)  To  show  the  power  of  the  nitrogen-gathering 
bacteria  to  supply  the  host  plant  with  nitrogen  taken 
from  the  air. 

This  experiment  is  believed  to  be  one  of  the  most 
valuable  and  practical  exercises  given  in  the  course, 
and  wherever  a  school  can  plan  to  conduct  it,  the 
classes  should  carry  it  through. 

References  :  Johnson,  How  Crops  Feed^  pp.  251-375.  Johnson, 
How  Crops  Grow^  pp.  126-220.  Snyder,  Soils  and  Fertilizers^ 
pp.   57-229.     Voorhees,  Fertilizers,  pp.  38-98. 


44  MANUAL  OF  AGRICULTURE 

Exercise  21 

Soil  Fertility 

To  SHOW   THAT   CERTAIN   PlANT   FoODS   ARE   ESSENTIAL 

Preparation  of  Pot  Cultures 

Use  clean  white  sifted  sand  in  5-liter  heavy  glass  battery  jars, 
having  1  centimeter  hole  within  1  centimeter  of  the  bottom.  Into 
the  hole  fit  a  drain  tube  made  of  glass  tubing  with  a  glass-wool 
filter  at  the  inner  end,  so  that  it  will  take  liquid  from  the  lowest 
place  in  the  jar.     Put  up  two  series  of  eight  of  these  pots. 

To  extract  the  sand,  fill  the  jar  within  1  centimeter  of  the 
top  with  dry  sifted  sand  and  add  to  this  dilute  sulphuric  acid 
(made  by  adding  100  cubic  centimeters  of  concentrated  chemically 
pure  sulphuric  acid  to  900  cubic  centimeters  of  ammonia-free 
water)  until  the  sand  is  saturated.  Let  stand  two  hours,  and 
then  add  ammonia-free  water,  allowing  the  drainage  to  flow  into 
a  second  jar  until  it  is  saturated.  Allow  this  jar  to  stand  two 
hours,  and  then  wash  both  with  ammonia-free  water  until  free 
of  acid,  as  shown  by  tests  with  litmus  paper.  In  this  way  any 
soluble  plant  food  is  removed  from  the  sand.  One  portion  of 
acid  extracts  two  jars.  The  sand  for  two  of  the  jars,  in  which 
experiments  are  to  be  made  to  show  the  effect  of  nitrogen-gather- 
ing bacteria,  is  first  heated  to  120° -130°  C.  for  half  an  hour, 
and  then  extracted  and  washed  as  above. 

Before  planting,  mix  with  the  sand  of  each  pot  10  grams  of 
pure  calcium  carbonate  to  neutralize  any  possible  acidity  remaining. 

In  making  applications  of  plant  food,  as  indicated  in  the  follow- 
ing table,  and  in  such  amounts  as  are  there  shown,  the  solutions  to 
be  applied  to  each  pot  are  to  be  mixed  together,  and  diluted  to 
1000  cubic  centimeters.     Mix  thoroughly,  and  apply  the  whole 


STUDIES  ABOUT  CROPS  45 

amount  to  the  pot,  allowing  any  water  present  to  be  forced  out 
throusrh  the  drain. 

The  first  application  of  the  plant-food  solutions  is  to  be  made 
at  the  time  of  planting,  the  second  three  weeks  later,  the  third  two 
weeks  later,  and  subsequent  applications  at  intervals  of  one  week, 
each  time  as  directed  above. 

Preparation  of  Plant-food  Solutions  ^ 

Solution  No.  1.  Nitrogen:  Dissolve  80  grams  of  ammonium 
nitrate  in  2500  cubic  centimeters  of  distilled  water.^  Use  10  cubic 
centimeters  per  pot. 

Solution  No.  2.  Phosphorus  :  Dissolve  25  grams  of  mono- 
calcium  phosphate  in  2500  cubic  centimeters  of  ammonia-free 
water.     Use  10  cubic  centimeters  per  pot. 

Solution  No.  3.  Potassium  :  Dissolve  50  grams  of  potassium 
sulphate  in  2500  cubic  centimeters  of  ammonia-free  water.  Use 
10  cubic  centimeters  per  pot. 

Solution  No.  4.  Magnesium  :  Dissolve  20  grams  of  magnesium 
sulphate  in  2500  cubic  centimeters  of  ammonia-free  water.  Use 
10  cubic  centimeters  per  pot. 

Solution  No.  5.  Iron  :  Dissolve  0.1  gram  ferric  chloride  in 
2500  cubic  centimeters  of  ammonia-free  water.  Use  1  cubic  cen- 
timeter per  pot. 

Prepare  these  solutions  carefully,  using  chemically  pure  salts,  and 
label  each  bottle. 

For  inoculating  the  sand  in  pot  8  with  bacteria,  obtain  about 
a  pound  of  soil  from  a  field  where  there  has  recently  been  growing 

1  The  instructor  in  chemistry  should  prepare  these  solutions  for 
Exercise  21. 

2  If  it  is  not  convenient  to  prepare  distilled  water  in  a  laboratory, 
pure  rain  water  may  be  used  in  this  experiment,  both  for  washing  the 
sand  and  watering  the  plants. 


46 


MANUAL  OF  AGRICULTURE 


Pot 

No. 

Preparation  of 
Sand. 

Plant  Food 
Added. 

Seeds  Planted. 

1 

Extract  and  wash 

None 

Corn  or  Soy  Beans 

2 

Extract  and  wash 

All  but  N 

Corn  or  Soy  Beans 

3 

Extract  and  wash 

All  but  P 

Corn  or  Soy  Beans 

4 

Extract  and  wash 

All  but  K 

Corn  or  Soy  Beans 

5 

None 

All 

Corn  or  Soy  Beans 

6 

None 

All 

Red  Clover,  Soy  Beans,  or 
Alfalfa 

7 

Heat,  extract,  and 

All  but  N 

Red  Clover,  Soy  Beans,  or 

wash 

Alfalfa 

8 

Heat,  extract,  and 

All  but  N 

Red  Clover,  Soy  Beans,  or 

wash 

Bacteria 

Alfalfa 

the  same  legume  which  is  to  be  used  in  this  experiment,  being 
sure  that  tubercles  were  present  on  the  roots.  Put  this  soil  in  a 
glass  fruit  jar  and  shake  thoroughly  with  about  one  quart  of  pure 
water.  Then  let  settle,  and  as  each  seed  is  planted  add  10  cubic 
centimeters  of  the  clear  liquid  before  covering  the  seed. 

Why  is  CaCO  3  added  ?     Why  are  two  of  the  pots  heated  ? 

Observe  each  week,  and  make  observations  about  differences  of 
growth  and  appearance. 

Thin  the  corn  and  bean  plants  to  three  in  each  pot  and  the  clover 
plants  and  alfalfa  to  ten. 

The  pots  should  stand  where  the  heat  and  light  conditions  are 
favorable  for  rapid  growth,  and  where  all  conditions  except  those 
controlled  in  the  application  of  plant-food  solutions  are  the  same  for 
every  plant. 

XIX.  —  Farming  in  Four-gallon  Pots 

In  Exercise  21  the  plants  were  grown  in  glass  bat- 
tery jars  filled  with  sand  from  which  all  plant  food  had 


STUDIES  ABOUT  CROPS  47 

been  extracted.  In  this  way  complete  control  of  the 
food  conditions  is  secured  in  studying  the  effects  of 
the  omission  of  any  particular  element,  because  it  was 
known  exactly  what  foods  were  furnished  for  the  plant 
and  what  was  lacking. 

Notice  that  in  the  experiments  the  tests  are  confined 
to  the  elements  nitrogen,  phosphorus,  and  potassium. 
The  reason  is  that  these  are  the  only  plant-food  ele- 
ments about  which  the  farmer  usually  needs  to  con- 
cern himself.  The  supply  of  carbon  dioxide  in  the 
air,  though  it  constitutes  not  more  than  6  parts  in 
10,000  of  the  atmosphere,  is  always  sufficient  to  meet 
the  needs  of  the  crop  for  carbon  and  oxygen,  and  the 
question  that  demands  the  attention  of  the  farmer  here 
is  only  that  of  preserving  an  abundant  and  healthy  leaf 
surface  for  his  growing  crops. 

From  the  water  contained  in  the  soil  the  hydrogen, 
and  more  oxygen,  are  obtained.  Sulphur,  magnesium, 
and  iron  are  used  by  plants  in  small  amounts  as  com- 
pared with  the  other  foods,  and  most  soils  contain 
enough  of  them  to  meet  crop  requirements  for  thou- 
sands of  years.  The  demand  for  calcium  as  a  plant 
food  is  not  large,  but  many  soils  are  more  or  less  acid, 
and  these  need  applications  of  lime  to  correct  this 
condition. 

In  the  case  of  nitrogen  and  phosphorus,  however, 
and  to  a  less  degree  in  Illinois,  of  potassium,  the  amounts 
of  these  elements  which  are  removed  from  the  soil  in 
large  crops,  as  compared  with  the  amounts  shown  by 
analyses  to  be  contained  in  the  surface  foot  of  most  of 


48  MANUAL  OF  AGRICULTURE 

these  soils,  are  so  great  that  maintaining  a  sufficient 
supply  of  some  or  all  of  these  three  elements  in  the 
soils  to  make  possible  the  raising  of  maximum  crops 
for  any  number  of  years  becomes  a  serious  problem  in 
soil  fertility. 

In  the  pot-culture  work  of  Exercise  22  regular  field 
soils  are  used,  the  object  being  to  test  the  needs  of  the 
soils  selected  for  whatever  crop  is  being  grown  in  re- 
spect to  the  three  plant  foods,  —  N,  P,  and  K. 

The  amounts  of  the  fertilizers  used  in  each  pot  are 
carefully  computed  on  the  basis  of  the  amounts  of  each 
element,  which  are  removed  from  an  acre  by  maximum 
crops,  i.e.  100  bushels  of  corn,  100  bushels  of  oats,  50 
bushels  of  wheat,  etc. 

Pots  1,  5,  and  10  are  used  as  checks  for  the  purpose 
of  comparison.  The  difference  between  the  yield  of 
pot  2  and  the  average  of  tlie  yields  of  pots  1,  5,  and  10 
will  indicate  the  soil's  need  of  nitrogen.  In  the  same 
way  the  question  is  asked  in  pot  3  for  phosphorus  and 
in  pot  4  for  potassium. 

It  may  happen  that  there  is  a  deficiency  of  plant 
food  in  two  elements,  or  even  three,  and  in  this  case 
there  can  be  no  material  increase  in  the  yields  until 
all  the  food  requirements  of  the  crop  are  met.  These 
points  will  be  settled  by  the  tests  made  in  pots  6,  7,  8, 
and  9. 

A  regular  plant  house  or  conservatory  is,  of  course, 
the  best  place  for  pot-culture  work,  but  these  exer- 
cises can  be  used  wherever  house  plants  can  be  grown. 
One  thing  is  very  essential  —  all  pots  must  be  given 


STUDIES  ABOUT  CROPS  49 

exactly  the  same  treatment  as  to  soil,  moisture,  heat, 
light,  and  planting,  the  only  condition  in  which  there 
is  a  difference  being  the  application  of  plant  food. 

References  :  Johnson,  How  Crops  Feed^  pp.  251-375.  Johnson, 
How  Crops  Grow,  pp.  126-220.  Snyder,  Soils  and  Fertilizers,  pp. 
67-229.     Voorhees,  Fertilizers,  pp.  38-98. 


Exercise  22 

Applications  of  Plant  Food  for  Crop  Production 

Use  four-gallon  earthenware  pots  in  series  of  ten  pots  for  each 
crop.  The  pots  should  have  holes  in  the  bottoms  for  drainage. 
Fill  another  pot  of  smaller  diameter,  heaping  it  full  of  sand,  and 
turn  over  this  the  pot  in  which  you  wish  to  make  a  hole,  so  that 
the  bottom  on  the  inside  rests  on  the  sand.  Then  with  a  sharp 
punch  and  a  few  light  blows  of  a  hammer  a  hole  can  be  easily  made. 

Fill  the  ten  pots  of  each  series  with  the  same  soil,  taking  it  from 
the  field  which  you  wish  to  test  for  the  crop  you  are  going  to  grow, 
as  oats,  barley,  wheat,  red  clover,  alfalfa,  sugar  beets,  or  any  of  the 
garden  crops. 

In  collecting  the  soil  for  the  pots,  take  it  from  the  upper 
seven  inches,  which  is  about  the  depth  of  the  usual  plow  line.^ 

Apply  the  plant  foods  according  to  directions  given  below  :  — 

1.  None  (check). 

2.  Nitrogen. 

1  To  make  the  conditions  follow  more  closely  field  conditions,  two 
collections  of  soil  should  be  made  as  follows :  Remove  the  soil  which 
is  to  be  used  in  the  experiment  to  the  depth  of  7  inches  and  place 
it  in  a  box.  Then  put  into  a  second  box  the  soil  underlying  this  in  the 
stratum  from  7  to  12  inches  below  the  surface.  In  filling  the  pots,  use 
soil  from  the  second  box  for  the  bottom,  and  on  5  inches  of  this 
place  the  surface  soil  from  the  first  box. 


50  MANUAL  OF  AGRICULTURE 

3.  Phosphorus. 

4.  Potassium. 

5.  None  (check). 

6.  Nitrogen,  phosphorus. 

7.  Nitrogen,  potassium. 

8.  Phosphorus,  potassium. 

9.  Nitrogen,  phosphorus,  potassium. 
10.  None  (check). 

For  applications  of  nitrogen,  use  ^  ounce  (16  grams)  of  dried 
blood  per  pot;  for  phosphorus,  use  ^  ounce  (8  grams)  of  steamed 
bone  meal;  for  potassium,  use  ^  ounce  (4  grams)  of  potassium 
chloride.  Mix  the  plant  food  thoroughly  with  the  soil  in  tlie  pots 
to  the  depth  of  7  inches,  a  few  days  before  the  seeds  are  to  be 
planted. 

The  pots  used  in  these  exercises  are  10^-  inches  in  diameter  and 
11|^  inches  deep  (inside  measurements).  This  gives  a  surface  area 
for  each  pot  of  about  y2Vo  ^^  ^^  a,CTe,  so  that  one  gram  application 
of  plant  food,  or  every  gram  of  jield  of  crop,  corresponds  to  one 
pound  per  square  rod,  or  160  pounds  per  acre. 

XX.  —  Experiment-field  Work  for  High  Schools 

The  University  of  Illinois  Experiment  Station  now 
has  twenty -three  experiment  fields  distributed  over  all 
parts  of  the  state.  Each  year  interest  in  the  work 
done  on  these  fields  has  increased,  not  alone  among 
those  directly  engaged  in  farming,  but  among  all  classes 
of  people  who  are  beginning  to  recognize  their  educa- 
tive value. 

Within  the  past  year  a  number  of  high  schools  have 
been  provided  with  land  to  be  used  in  teaching  agri- 
culture.    These   school   fields   generally  range  in  size 


STUDIES  ABOUT  CROPS  51 

from  five  to  ten  acres.  In  some  cases  the  land  has  been 
given  to  the  school,  in  others  it  has  been  bought  or 
rented  by  the  district,  and  in  still  other  cases  a  land- 
owner interested  in  having  agriculture  taught  in  the 
school  has  donated  the  use  of  as  much  land  as  the  school 
needs  for  the  purpose. 

Dr.  C.  G.  Hopkins,  Professor  of  Agronomy,  Univer- 
sity of  Illinois,  and  Chief  of  Agronomy  of  the  Agri- 
cultural Experiment  Station,  offers  to  assist  any  schools 
in  the  state  that  wish  to  establish  experiment  plots  in 
the  laying  out  of  their  plots  and  the  planning  of  the 
work  to  be  done  on  them. 

Already  two  or  three  high  schools  have  availed  them- 
selves of  this  offer,  and  their  fields  have  been  plotted  for 
school  work.  There  is  reason  to  believe  that  popular 
sentiment  favoring  this  branch  of  school  work  is  so 
strong  that  it  will  not  be  difficult  for  any  high  school 
to  secure  enough  land  to  establish  an  experiment  field 
to  be  used  in  connection  with  its  courses  in  agriculture. 

This  work  with  the  plots  does  not  duplicate  the  pot- 
culture  work  given  in  Exercise  22,  though  each  may  be 
regarded,  in  a  way,  as  a  complement  of  the  other. 

In  the  work  with  the  pots  certain  tests  may  be  made 
that  require  a  more  complete  control  of  conditions  than 
can  be  secured  in  field  work.  On  the  other  hand,  in 
the  experiments  on  the  plots,  the  crops  are  grown  under 
the  natural  conditions  with  which  the  farmer  deals,  and 
on  a  scale  sufficiently  large  to  make  it  possible  to  com- 
pare results  with  those  on  the  surrounding  farms.  If 
the  work  is  carefully  planned  in  the  beginning,  and  then 


52  MANUAL  OF  AGRICULTURE 

the  plans  are  followed  and  the  results  obtained  each 
year  are  kept  as  a  permanent  record,  the  experiment 
plots  will  every  year  increase  in  interest  and  usefulness 
as  a  part  of  the  school  work  in  agriculture. 

The  outlines  of  the  work  given  in  Exercises  22  and  23 
were  prepared  by  Dr.  Hopkins,  and  were  published  in  a 
leaflet  a  few  years  ago.  Exercise  21  is  taken  from 
Laboratory  Manual  for  Soil  Fertility^  by  Dr.  Hopkins 
and  Professor  J.  H.  Petti t,  where  it  is  given  as  Practices 
16  and  17. 

References  :  Johnson,  How  Crops  Feed,  pp.  251-375.  Johnson, 
How  Crops  Grow,  pp.  126-220.  Snyder,  iSoils  and  Fertilizers,  pp. 
57-229.     Voorhees,  Fertilizers,  pp.   38-98. 

Exercise  23 

Plot-culture  Tests  to  Determine  the  Plant  Food  Requirements 

of  the  Soil 

The  size  of  the  plots  to  be  used  will  be  determined  by  the  amount 
of  land  available  for  this  work. 

Where  the  area  is  restricted,  the  plots  may  be  laid  off  in  rec- 
tangles ^  rod  by  2  rods  and  separated  from  each  other  by  sunken 
paths  not  less  than  2  feet  wide.  This  will  give  each  plot  an  area 
of  one  square  rod  (yj^  of  an  acre).  If  the  school  possesses  more 
land,  larger  plots  up  to  tenth  acres  (2  rods  wide  and  16  rods  long), 
with  half-rod  strips  separating  them,  may  be  laid  off,  as  is  done  on 
the  experimental  fields  at  the  University. 

The  plant-food  applications  for  the  smaller  plots  (one  square 
rod),  to  be  made  annually,  are  as  follows  :  — 

Plot  No.  1.    None  (check). 

Plot  No.  2.    Nitrogen. 


STUDIES  ABOUT  CROPS  53 

Plot  No.     3,    Phosphorus. 

Plot  No.     4.    Potassium. 

Plot  No.    5.    None  (check). 

Plot  No.     6.    Nitrogen,  phosphorus. 

Plot  No.     7.    Nitrogen,  potassium. 

Plot  No.     8.    Phosphorus,  potassium. 

Plot  No.     9.    Nitrogen,  phosphorus,  potassium. 

Plot  No.  10.    None  (check). 

Apply  the  nitrogen  in  the  form  of  dried  blood,  16  pounds  per 
square  rod  ;  phosphorus  as  steamed  bone  meal,  8  pounds  per  square 
rod;  potassium  as  potassium  chlorid,  4  pounds  per  square  rod. 
The  plant  foods  should  be  well  worked  into  the  soil  to  the  depth 
of  about  7  inches  a  few  days  before  planting,  care  being  taken 
not  to  mix  the  soils  from  adjacent  plots. 

Several  different  field  and-  garden  crops  should  be  planted  in  rows 
across  all  of  the  ten  plots.  Oats,  barley,  wheat,  clover,  alfalfa,  etc., 
can  be  planted  in  rows  8  inches  apart,  dropping  the  seeds  about  1 
inch  apart  in  the  row ;  radishes,  lettuce,  carrots,  beets,  peas,  etc., 
in  rows  16  inches  apart;  sweet  corn,  potatoes,  cowpeas,  soy  beans, 
etc.,  in  rows  32  inches  apart;  field  corn  in  rows  40  inches  apart; 
and  cucumbers  and  melons  64  inches  apart. 

A  marker  with  five  runners  16  inches  apart  is  easily  made  of 
boards,  and  it  will  serve  to  mark  good  straight  rows  across  all  of 
the  plots  for  all  crops. 

By  this  system  of  planting  every  crop  will  be  represented  on 
every  plot,  and  the  effect  of  all  of  the  different  kinds  of  soil  treat- 
ment can  be  noted  on  each  crop. 

If  the  complete  experiment  cannot  be  undertaken,  a  fairly  satis- 
factory experiment  can  be  made  by  using  only  the  first  five  pots 
or  plots. 

In  planning  these  soil-fertility  experiments,  it  is  well  to  bear  in 
mind  that  very  sandy  soil  is  likely  to  be  most  deficient  in  nitrogen. 


54  MANUAL  OF  AGRICULTURE 

In  ordinary  Illinois  soil,  especially  that  which  has  been  under  cul- 
tivation for  many  years  with  clover  in  rotations,  the  element  phos- 
phorus is  most  deficient.  In  peaty  soils,  potassium  is  most  de- 
ficient. 

In  drawing  conclusions  from  results  which  may  be  obtained  in 
these  experiments,  it  should  be  understood  that  while  we  may  ap- 
ply purchased  nitrogen  in  order  to  obtain  information  quickly  as 
to  the  needs  of  the  soil,  the  nitrogen  should  be  obtained  in  all  gen- 
eral farming  by  the  slower  process  of  growing  leguminous  crops 
which,  when  provided  with  the  proper  bacteria,  can  get  nitrogen 
from  the  air. 

The  three  plant-food  elements,  nitrogen,  phosphorus,  and  potas- 
sium, are  contained  in  most  soils  in  rather  small  amounts.  In- 
deed, it  often  happens  that  the  soil  furnishes  so  little  of  one  or 
more  of  these  elements  that  the  plant  suffers  for  that  kind  of  food. 
In  such  cases  we  can  grow  larger  crops  by  giving  the  plant  the 
food  it  needs. 

To  find  what  elements  of  plant  food  are  most  deficient  in  the 
soil,  we  should  experiment  and  see  what  effect  is  produced  on 
the  growth  of  plants  by  adding  different  plant-food  elements  to 
the  soil. 

For  nitrogen,   dried  blood  should  be  applied.     This  contains 

from  12  to  14  per  cent  of  nitrogen  in  a  form  which  is  not  likely  to 

injure  the  plant,  even  if  used  in  some  excess.     A  100-pound  bag 

'  of  ground  dried  blood  can  be  obtained  from  Swift  &  Company, 

Union  Stock  Yards,  Chicago,  for  about  $2.50. 

For  phosphorus,  steamed  bone  meal  should  be  applied.  The 
best  steamed  bone  meal  contains  from  12  to  14  per  cent  of  the 
element  phosphorus  in  a  very  good  form  for  plants.  A  100-pound 
bag  of  extra  fine  ground  steamed  bone  meal  ("  Big  Six  "  brand) 
can  be  obtained  from  Morris  &  Company,  Union  Stock  Yards, 
Chicago,  for  about  $1.25. 


STUDIES   ABOUT  CROPS  55 

For  potassium,  use  potassium  chlorid.  This  is  a  salt  which 
usually  contains  from  40  to  42  per  cent  of  the  element  potassium. 
A  100-pound,  bag  of  potassium  chlorid  can  be  obtained  from 
Armour  Fertilizer  Works,  Union  Stock  Yards,  Chicago,  for  about 
12.50. 

The  Armour  Fertilizer  Works,  Union  Stock  Yards,  Chicago, 
have  agreed  to  furnish  a  one-pound  package  of  potassium  chlorid, 
a  two-pound  package  of  fine  ground  steamed  bone  meal,  and  a 
four-pound  package  of  ground  dried  blood  for  a  total  charge  of 
seventy-five  cents,  the  purchaser  to  pay  express  charges. 

These  quantities  are  ample  for  pot-culture  experiments. 

XXI.  —  Questions  relating  to  the  Seeding  of  Crops 

There  is  found  among  farmers  to-day  a  great  differ- 
ence of  opinion  —  or  a  great  indefiniteness  of  opinion 
— about  the  quantity  of  seed  per  acre  in  the  various  crops 
that  should  be  sown  to  give  best  results.  In  the  case  of 
oats,  for  instance,  is  it  better  to  make  a  thin  seeding  to  en- 
courage the  tendency  of  the  plants  to  tiller,  or  will  heavier 
yields  of  better  quality  of  grain  be  secured  by  planting 
so  thickly  that  each  seed  will  produce  but  a  single 
stalk  and  head  ?  There  are  as  strong  adherents  to  the 
one  practice  as  to  the  other. 

It  may  be  that  experimental  work  on  such  subjects  by 
school  classes  in  agriculture  will  add  little  to  the  sum  of 
knowledge  which  we  already  have  about  it;  but  it  is 
by  becoming  interested  in  work  of  this  kind  that  men 
are  trained  to  think  independently  and  to  form  definite 
opinions,  supported  by  scientific  principles  and  personal 
experience.     Such  work  as  is  given  in  Exercises  24  and 


56  MANUAL   OF  AGRICULTURE 

25  has  been  found  very  profitable  in  the  agricultural 
schools  in  Canada. 

The  work  is  not  at  all  difficult  for  a  class  to  handle, 
but  it  will  require  care  and  thought.  The  seed  should 
first  be  tested  to  determine  its  vitality.  The  pupils 
will  find  that  some  samples  of  oats  will  contain  very 
many  more  grains  in  a  bushel  than  others.  This  raises 
other  questions  for  them  to  consider.  For  example  :  — 
Shall  more  or  less  seed  be  sown  on  fertile  soil  than  on 
one  that  contains  less  plant  food  ?  Such  problems  con- 
cern alike  the  farmer  and  the  student. 

Eeference  :  Hunt,  The  Cereals  in  America^  p.  302. 

Exercise  24 

Crop  Production:  Oats 

To  Determine  what  Amount  of  Seed  per  Acre  gives 

Best  Results 

On  a  series  of  10  plots  of  one  square  rod  each,  in  which  all  con- 
ditions are  similar,  except  the  amount  of  seed  used,  make  seedings 
of  oats  as  follows  :  — 

Plot    1.    Sow    3i  ounces  (rate  of    1  bushel  per  acre). 

Plot    2.    Sow    44  ounces  (rate  of  11  bushels  per  acre). 

Plot    3.    Sow    44  ounces  (rate  of    2  bushels  per  acre). 

Plot    4.    Sow      8  ounces  (rate  of  2\  bushels  per  acre). 

Plot    5.    Sow    9 1  ounces  (rate  of    3  bushels  per  acre). 

Plot    6.    Sow  114-  ounces  (rate  of  3i-  bushels  per  acre). 

Plot    7.    Sow  124  ounces  (rate  of    4  bushels  per  acre). 

Plot    8.    Sow  14|  ounces  (rate  of  41-  bushels  per  acre). 

Plot    9.    Sow  IG    ounces  (rate  of    5  bushels  per  acre). 

Plot  10.    Sow  17|  ounces  (rate  of  5^  bushels  per  acre). 


STUDIES   ABOUT   CROPS  57 

Make  the  drills  8  inches  apart  and  cover  1|-  to  2  inches  deep. 
During  the  season  of  growth  observe  the  differences  in  the  tendency 
of  the  plants  to  "  stool  "  due  to  thickness  of  planting. 

When  ripe,  harvest  each  plot  separately  and  thresh  with  a  flail. 
Weigh  and  record  the  yields  of  each  plot,  giving  their  acre  equiva- 
lents. 

XXII.  —  Methods  of  Sowing  Grains 

Another  question  relating  to  the  growing  of  oats  and 
other  spring  grains,  which  still  remains  unsettled  in  the 
minds  of  many  farmers,  is  whether  drilling  or  broad- 
casting is  the  better  way  to  sow  the  seeds.  The  one 
method  insures  a  more  perfect  covering  of  the  seed  at 
a  uniform  depth ;  the  other  may  give  a  more  even  dis- 
tribution of  the  grain  over  the  whole  surface  at  less 
cost  for  labor  and  machinery.  It  is  a  good  experiment 
for  classes  in  agriculture  to  work  on.  Of  course,  the 
results  of  a  single  season  cannot  settle  the  matter. 
There  are  so  many  conditions  that  affect  the  growing 
of  a  crop  which  are  seasonal,  and  differ  from  year  to 
year,  that  it  will  require  the  results  of  many  tests  to 
give  any  reliable  basis  on  which  to  form  conclusions  ; 
but  if  these  experiments  were  continued  in  a  school 
year  after  year,  and  the  records  were  taken  accurately 
and  left  for  succeedinsc  classes  to  use  and  extend,  it  is 
certain  the  work  could  be  made  worth  while. 

Keferexces  :  Hunt,  The  Cereals  in  America,  pp.  131,  296,  304. 
Dondlinger,  The  Book  of  Wheat,  pp.  65-69. 


58  MANUAL  OF  AGRICULTURE 

Exercise  25 

Crop  Production :  Oats 
Test  of  Drilling  versus  Broadcasting 

Lay  off  four  plots  of  one  square  rod  each  and  prepare  them  all 
for  seeding  in  the  same  way,  then  sow  oats  as  follows :  — 

Plot  1.    Sow  4^  ounces  (1|-  bushels  per  acre)  in  drills  8  inches 
apart  and  cover  1^2  inches  deep. 

Plot  2.    Sow  4|  ounces  (1^  bushels  per  acre)  broadcast  and  cover 
with  a  garden  rake. 

Plot  3.    Sow  6|-  ounces  (2  bushels  per  acre)  in  drills  8  inches 
apart  and  cover  1^2  inches  deep. 

Plot  4.    Sow  6f  ounces  (2  bushels  per  acre)  broadcast  and  cover 
with  a  garden  rake. 

Observe  differences  in  growth  between  the  oats  drilled  and  those 
sown  broadcast. 

Harvest  and  thresh  crops  on  each  plot  separately  and  record  the 
yields,  giving  results  in  acre  equivalents.     Write  conclusions. 

XXIII.  —  Special  Treatment  of  Seed 

The  farmer  who  would  succeed  in  the  work  of  grow- 
ing crops  must  not  only  know  how  to  prepare  and  treat 
the  soil,  how  to  breed  and  select  seed,  how  to  plant  the 
seed  and  cultivate  the  crop,  but  he  must  also  know 
how  to  protect  the  growing  plants  from  the  many  forms 
of  insect  enemies  and  fungus  diseases  which  seem  to  be 
increasing  from  year  to  year  in  numbers  and  destruc- 
tiveness. 

A  disease  which  is  very  common  in  oat  fields  and 
much  more  serious  in  its  effects  upon  the  yield  of  the 


STUDIES  ABOUT  CROPS  59 

crop  than  most  farmers  realize  is  smut.  There  are  two 
forms  of  this  disease  :  loose  smut,  which  attacks  the 
whole  head  and  turns  it  into  a  black  mass  of  spores ; 
and  closed  smut,  which  affects  only  the  kernels,  and  is 
not  so  easily  seen. 

If  the  farmer  were  helpless  in  combating  this  enemy, 
it  might  be  well  to  let  him  remain  ignorant  of  the 
amount  of  the  loss  it  causes  him.  Professor  Zavitz,  of 
the  Ontario  Agricultural  College,  who  has  conducted 
experiments  for  many  years  in  growing  and  improving 
oats,  says  that  in  many  fields  the  loss  from  smut 
amounts  to  40  per  cent  or  more.  A  few  years  ago  a 
careful  investigation  of  the  oat  fields  of  Wisconsin  was 
made  through  the  assistance  of  graduates  of  the  College 
of  Agriculture,  and  it  was  found  that  17  per  cent  of  the 
crop  that  year  was  destroyed  by  smut. 

And  yet  there  are  two  simple  and  inexpensive  treat- 
ments by  which  this  disease  can  be  completely  pre- 
vented. It  is  the  purpose  of  Exercise  26  to  familiarize 
the  students  with  these  methods  of  treating  the  seed 
which  are  now  known  to  be  effective  in  safeguarding 
the  crop  from  smut.  There  would  be  an  increase  to 
the  country  annually  of  millions  of  bushels  of  oats  if 
the  farmers  could  be  taught  to  use  one  of  them. 

Since  the  spores  of  the  fungi  which  cause  the  smut 
in  oats  are  attached  to  the  seed  and  develop  in  the  grow- 
ing stem  of  the  plant  until  the  head  appears  and  is 
ready  for  their  attack  upon  it,  any  treatment  of  the 
seed  which  will  kill  these  spores  and  not  injure  the 
vitality  of  the  grain  for  seed  purposes  will  be  effective, 


60  MANUAL   OF  AGRICULTURE 

and  two  such  treatments  are  given  for  practice  in  Ex- 
ercise 26. 

Students  will  be  impressed  with  the  extent  and 
seriousness  of  this  disease  if  they  make  inspections  of 
oat  fields  to  determine  the  per  cent  of  the  crop  that  is 
affected  by  it.  Let  each  student  provide  himself  with 
a  lath  frame  having  an  area  of  one  square  foot.  In 
different  parts  of  the  field  in  which  the  examination  is 
being  made,  place  this  frame  on  the  ground,  count  the 
numbers  of  stems  of  oats  inclosed  by  the  sides  of  the 
frame,  and  also  the  number  of  stems  bearing  heads 
affected  by  smut.  In  this  way,  by  finding  the  average 
of  the  fractions  showing  the  proportion  of  diseased 
heads  to  sound  ones,  a  fairly  accurate  determination 
of  the  per  cent  of  loss  in  this  oat  crop  caused  by  smut 
can  be  made. 

On  fields  or  plots  where  treated  seed  is  used,  leave  a 
narrow  strip  for  comparison,  and  here  sow  untreated 
seed.  Then  find  the  per  cents  of  diseased  heads  of  oats 
where  the  two  kinds  of  seeds  were  used.  A  comparison 
of  these  records  should  be  conclusive  proof  of  the  value 
of  treating  seed  oats  for  smut. 

Exercise  26 

Treating  Seed  Oats  for  Smut 

First  Method 

On  a  tight  floor  spread  a  few  bushels  of  the  seed  to  be  treated. 
Make  a  sohition  of  concentrated  formalin  (a  forty  per  cent  solu- 
tion of  formaldehyde),  using  one  pint  of  the  formalin  to  forty  gal- 


STUDIES  ABOUT  CROPS  61 

Ions  of  water.  Apply  this  solution  to  the  oats  with  an  ordinary- 
sprinkling  pot,  wetting  the  top  of  the  pile,  then  stirring  the  grain 
with  a  shovel  and  continuing  the  sprinkling  and  stirring  until 
every  kernel  is  thoroughly  moistened.  Now  shovel  the  grain  into 
a  pile  and  cover  with  a  blanket  or  sacks  for  about  12  hours  to 
prevent  too  rapid  evaporation  of  the  formalin. 

Then  uncover  and  shovel  the  pile  over  two  or  three  times,  and 
the  seed  will  be  dry  enough  to  sow. 

The  price  of  formalin  is  from  sixty  to  eighty  cents  a  pint,  and  the 
treatment  of  the  seed  will  cost  from  two  to  four  cents  a  bushel. 

Second  Method 

Have  two  vessels  —  large  tubs  or  barrels  are  best  —  and  fill  them 
nearly  full  of  hot  water.  Let  the  water  in  one  vessel  be  at  a 
temperature  of  110°-120°  F.,  and  in  the  other  132°-133°  F. 
Have  near  at  hand  a  bucket  of  cold  water  and  a  kettle  of 
boiling  water  to  use  in  keeping  the  liquid  in  the  large  vessels 
at  the  required  temperatures. 

Put  a  bushel  of  oats  in  a  sack  and  dip  it  into  the  water  at 
110°-120°  F.  Leave  it  a  minute  for  the  mass  to  become  warmed 
through,  then  change  it  to  the  other  vessel  of  water  at  132°- 
133°  F.  Keep  a  thermometer  in  the  water,  and  should  the 
temperature  rise  or  fall,  control  it  by  adding  cold  or  hot  water, 
as  may  be  needed. 

Every  two  or  three  minutes  raise  the  sack  of  grain  out  of  the 
water  and  lower  it  again.  This  will  aid  to  saturate  the  whole  mass 
thoroughly. 

Keep  the  seed  in  the  hot  water  for  ten  minutes,  then  spread  out 
on  a  floor  and  dry  sufiiciently  for  sowing.  Repeat  with  as  many 
bushels  as  are  needed.  Each  of  these  methods  of  treating  the  seed 
for  smut,  if  the  work  is  done  thoroughly,  will  kill  aU  the  pores  and 
completely  protect  the  crop  from  this  disease. 


62  MANUAL  OF  AGRICULTURE 

XXIV.  —  Studies  with  Corn 

In  many  ways  corn  is  much  the  most  satisfactory  of 
all  crops  for  class  study  and  experiment  work.  It  is 
planted  and  makes  considerable  growth  in  the  spring 
before  the  close  of  the  school  year,  and  its  season  is  so 
long  that  it  is  still  standing  and  maturing  its  grain 
when  school  work  begins  again  in  the  fall. 

Being  planted  in  open  rows,  it  is  easy  of  access  for 
observation  and  experiment  work.  Cultivation  plays  a 
larger  part  in  the  growing  of  corn  than  it  does  with 
our  other  important  cereals,  and  for  this  reason  the  suc- 
cess of  the  crop  is  more  dependent  upon  the  care  it  re- 
ceives during  the  growing  season  than  in  the  case  of 
the  other  grains. 

Moreover,  it  is  the  greatest  wealth-producing  crop  in 
the  United  States;  and  hence  especial  attention  is  being 
given  to  the  improvement,  selection,  and  care  of  seed 
and  to  methods  of  cultivation. 

The  structure  of  the  plant  also  lends  interest  to  its 
study.  The  fact  that  the  stamens,  which  are  the  pollen- 
bearing  organs  of  the  corn  plant,  are  produced  on  the 
top  part  of  the  stalk,  —  the  tassel,  —  while  the  pistils, 
the  other  essential  organs  of  the  flower,  —  in  corn  called 
the  silk,  — are  where  the  ear  is  borne  makes  it  possible 
for  the  corn  breeder  to  control  the  matter  of  inbreeding 
and  self-fertilization  and  to  a  large  degree  determine 
the  parentage  of  each  kernel  of  corn. 

In  the  case  of  corn,  as  with  oats,  wheat,  and  other 
small  grains,  there  is  much  uncertainty  of  opinion  as  to 


STUDIES  ABOUT  CROPS  63 

the  proper  thickness  of  planting  and  width  of  rows. 
Many  experiment  stations  are  working  on  this  problem, 
and  the  results  of  their  tests  will  be  published  later. 
Probably  the  particular  value  that  work  such  as  that 
outlined  in  Exercise  27  will  have  in  school  agriculture 
will  come  from  directing  attention  to  the  importance 
of  the  farmer's  having  some  definite  knowledge  on  such 
questions  as  a  guide  to  farm  practices,  and  in  the  train- 
ing that  it  gives  to  those  who  are  to  manage  farms  and 
who  should  know  how  to  settle  these  problems  for 
themselves.  These  are  matters  that  directly  affect  the 
profits  of  farming;  and  it  is  good  training  to  teach  the 
pupils  that  agriculture  is  a  business  full  of  problems  to 
be  settled,  and  that  those  who  make  it  a  success  must 
know  how  to  handle  them. 

In  considering  the  thickness  of  planting  and  the  best 
distance  between  the  hills,  try  to  determine  whether  it 
is  largely  a  question  of  sufficient  supply  of  plant  food 
in  the  soil,  a  more  even  distribution  of  corn  roots 
through  the.  whole  area  covered,  or  the  best  exposure  of 
the  plants  to  sunlight  and  air. 

Keference  :  Hunt,  The  Cereals  in  America^  pp.  227-234. 


Exercise  27 

Crop  Production :  Corn 

To  Determine  how  close  to  plant  Corn 

Prepare  five  plots  of  one  square  rod  each  for  corn,  making  the 
conditions  alike  for  all  plots  ;  then  plant  as  follows  :  — 


64  MANUAL  OF  AGRICULTURE  \ 

Plot  1 .  Hills  4  feet  x  3  feet,  4  stalks  in  a  hill. 

Plot  2.  Hills  4  feet  x  1  foot,  1  stalk  in  a  hill. 

Plot  3.  Hills  31  feet  x  31  feet,  3  stalks  in  a  hill. 

Plot  4.  Hills  3  feet  X  3  feet,  3  stalks  in  a  hill. 

Plot  5.  Hills  3  feet  X  3  feet,  2  stalks  in  a  hill. 

Before  planting,  the  seed  should  be  carefully  tested  for  ger- 
mination, and  on  plots  (1),  (3),  (4)  plant  five  grains,  and  a  few  days 
after  the  corn  is  through  the  ground,  thin  to  the  required  num- 
ber.    On  plots  (2)  and  (5)  plant  three  grains,  and  thin  as  required. 

When  the  corn  is  mature,  husk  and  weigh,  giving  the  yields  of 
each  plot  reduced  to  acre  equivalents. 


XXV.  —  Problems  in  Cultivating  Corn 

In  growing  corn  it  is  an  almost  universal  practice  to 
cultivate  the  soil  between  the  hills,  from  the  time  the 
plants  are  through  the  ground  so  that  the  rows  can  be 
seen  until  they  are  too  large  to  permit  a  team  to  be 
used,  and  then  in  many  cases  some  cultivation  is  done 
later  by  hand  with  the  hoe. 

The  method  of  cultivation  employed  to-day  and  the 
implements  that  are  used  in  cultivating  corn  now  differ 
widely  from  those  of  a  generation  ago  ;  but  in  those 
days,  as  at  the  present  time,  a  large  factor  in  the  cost 
of  growing  the  crop  was  in  the  tillage  that  was  believed 
to  be  necessary  while  the  corn  was  growing. 

Considering  the  importance  of  this  item  of  expense, 
and  the  fact  that  the  sort  of  cultivation  that  was  once 
practiced  in  corn  growing  is  now  almost  wholly  dis- 
carded, we  may  well  consider  what  is  the  real  purpose 


STUDIES  ABOUT  CROPS  65 

of  the  work  given  to  the  cultivation  of  corn  and  what 
would  result  if  some  or  all  of  this  work  were  omitted. 

In  Exercise  28  the  difference  in  the  treatments  of 
plots  1  and  3  is  to  see  whether  the  early  preparation 
of  the  soil,  as  in  plot  1,  will  result  in  storing  a  larger 
supply  of  water  in  the  soil  to  the  advantage  of  the  crop 
so  as  to  make  it  profitable  to  apply  this  extra  labor. 

In  plot  2,  compared  with  1,  and  plot  4,  compared 
with  3,  the  test  is  made  to  see  whether  the  frequent 
cultivations  usually  given  to  the  corn  field  are  valuable 
because  they  destroy  the  weeds  or  because  they  stir  the 
surface  soil. 

And  the  treatment  of  plot  5,  when  the  results  are 
compared  with  those  of  plots  3  and  4,  should  show 
whether  it  is  very  important  to  keep  the  weeds  from 
growing  with  the  crop. 

This  work  should  be  repeated  each  year,  recording 
the  results  together  with  the  special  weather  conditions 
of  the  season.  If  a  number  of  schools  in  the  country 
carry  on  the  same  experiment,  there  will  be  increased 
interest  and  value  in  the  results  obtained. 

References  :  Hunt,  The  Cereals  in  America,  pp.  218-225. 
Orange  Judd  Co.,   The  Book  of  Corn,  pp.  87-95,  115-127,  167-191. 

Exercise  28 

Crop  Production :  Corn 
To  SHOW  Effects  of  Different  Methods  of  Tillage 

Use  5  plots  of  one  square  rod  each  (^  rod  X  2  rods),  planting 
on  each  plot  3  rows  of  corn,  running  lengthwise  of  the  plots,  3  feet 


66  MANUAL   OF  AGRICULTURE 

apart,  the  hills  being  3^  feet  apart  in  the  row,  3  stalks  to  each 
hill. 

Prepare  the  soil  for  planting  as  follows  :  — 

Plot  1.  Plow  (or  spade)  as  early  in  the  spring  as  the  soil  is  in 
condition  to  work,  and  thoroughly  cultivate  the  surface  each  week 
until  the  time  of  planting.  Keep  the  plot  free  from  weeds,  and  a 
loose  surface  mulch  until  the  ground  is  thoroughly  shaded  by  the 
corn. 

Plot  2.  Prepare  the  ground  for  planting  as  in  plot  1,  but  after 
the  corn  is  planted  do  not  stir  the  ground  at  all.  Keep  the  weeds 
down  by  shaving  them  off  with  a  sharp  hoe. 

Plot  3.  Do  not  plow  (or  spade)  the  ground  until  just  before 
planting.  Then  cultivate  the  plot  through  the  season  carefully,  as 
in  the  case  of  plot  1 . 

Plot  4.  Do  not  prepare  the  ground  until  ready  for  planting. 
After  planting,  treat  the  plot  in  the  same  way  as  was  done  with 
plot  2,  merely  shaving  oft'  the  weeds  at  the  surface. 

Plot  5.  Prepare  the  ground  for  planting  as  was  done  for  plots 
3  and  4.  After  planting,  do  nothing  more,  allowing  the  weeds  to 
grow  and  the  soil  to  remain  packed  and  uncultivated. 

During  the  season  make  notes  from  time  to  time  of  the  appear- 
ance of  the  crops  on  each  plot.  Take  measurements  of  the  height 
of  plants  and  record  them  and  other  evidences  of  relative  vigor  of 
the  crops  on  each  plot.  Where  were  the  signs  of  lack  of  sufficient 
moisture  most  apparent  ? 

At  the  proper  season  husk  the  corn  on  each  plot,  weigh  and  re- 
cord the  crops,  reducing  them  to  acre  equivalents. 

XXVI.  —  How  Moisture  may  be  saved  for  the 

Corn  Crop 

It  is  the  general  belief  that  one  of  the  chief  benefits 
resulting  to  the  crop  from  the  frequent  stirring  of  the 


STUDIES  ABOUT  CROPS  67 

surface  of  the  soil  is  due  to  the  conservation  of  the  mois- 
ture content  of  the  soil  by  means  of  the  loose  dust  mulch. 

The  tests  to  be  made  in  Exercise  29  are  to  determine 
how  great  are  the  differences  in  the  amounts  of  water 
stored  in  the  upper  40  inches  of  the  soil  due  to  the 
various  cultural  treatments  that  were  used. 

The  differences  in  the  amounts  of  water  found  on  the 
several  plots  should  be  expressed  in  acre-inches  and 
tons  per  acre. 

Reference  :  Hunt,  The  Cereals  in  America^  pp.  235-242. 

Exercise  29 

Determination  of  the  Water  Content  of  the  Soil  on  Each 

Plot  for  Exercise  28 

Mark  and  weigh  30  soil  pans,  as  in  Exercises  2  and  3.  (Run 
the  determinations  in  dupHcates.)  Takes  samples  of  surface,  sub- 
surface, and  subsoil  from  each  plot  according  to  directions  for  Ex- 
ercise 2.  Weigh  out  100  grams  of  soil  in  each  pan,  and  let  them 
dry  at  room  temperature  for  a  week.  Weigh  again,  and  the  loss  of 
weight  will  be  the  number  of  grams  of  capillary  moisture  con- 
tained in  the  soil.  A  comparison  of  the  amounts  of  water  found 
in  the  soils  of  the  different  plots  will  impress  the  value  of  tillage  in 
the  conservation  of  moisture. 

Do  the  results  show  the  value  of  preparing  the  ground  for  the 
crop  as  early  as  possible? 

How  much  water  has  been  stolen  from  the  plots  by  the  weeds  % 

XXVII.  —  Growth  of  Corn  Roots 

By  far  the  greater  part  of  the  labor  expended  in 
growing  the  cereal  crops  is  directed  to  bettering  those 


68  MANUAL   OF  AGRICULTURE 

conditions  which  affect  the  environment  of  the  roots, 
and  yet  this  is  the  part  of  the  plant  about  which  farmers 
generally  have  the  most  indefinite  and  incorrect  con- 
ceptions. 

The  root  naturally  is  the  least  conspicuous  portion 
of  the  plant,  and  it  is  difficult  to  remove  it  from  the 
soil  without  leaving  behind  so  much  of  the  delicate 
fibers  and  root  hairs  that  one  usually  gets  a  very  imper- 
fect conception  of  the  position  which  a  plant's  roots 
occupy  in  the  soil  and  the  extent  of  area  that  they 
cover. 

To  those  who  have  not  investigated  this  subject,  it 
will  be  a  surprise  to  learn  how  rapidly  corn  roots  grow 
in  a  fertile  soil  and  how  soon  they  spread  laterally  to 
the  center  of  the  rows. 

How  deep  the  cultivation  can  safely  be  made  between 
the  rows  of  corn,  and  how  close  to  the  hill  it  is  wise  to 
stir  the  soil,  even  to  the  depth  of  two  or  three  inches* 
are  questions  about  which  farmers  differ. 

Exercise  30  is  given  for  the  purpose  of  directing  at- 
tention to  a  more  thorough  study  of  the  root  systems  of 
plants  and  the  habits  of  root  growth,  in  order  that  the 
farmer  may  possess  some  reasonable  basis  for  his  deci- 
sions in  the  matter  of  the  cultivation  of  his  crops. 

Such  exercises  as  this  will  necessarily  extend  into  the 
summer  vacation  ;  but  some  pupils  in  some  schools 
may  become  so  interested  that  they  will  want  to  carry 
on  the  investigation  during  the  summer  and  make  their 
reports-  at  the  opening  of  the  next  year  of  school.  In 
fact,  an  interest  which  will  carry  this  work  into  the 


STUDIES  ABOUT  CROPS  69 

homes  of  ths  pupils  and  connect  it  with  the  work  on 
the  farm  and  in  the  garden  must  be  the  real  test  of  the 
school's  success  in  teaching  agriculture. 

References  :  Hunt,  The  Cereals  in  America^  pp.  336-340.     Orange 
Judd  Co.,  Tlie  Book  of  Corn,  pp.  115-127. 


EXEKCISE   30 

Crop  Production:  Corn 
A  Study  of  Corn  Roots 

Plant  one  plot  of  corn  to  be  used  for  the  purpose  of  investiga- 
tions of  the  roots  and  the  effects  of  deep  and  shallow  cultivation. 

Beginning  one  week  after  the  corn  appears  above  the  ground, 
carefully  remove  a  hill  so  as  to  preserve  all  the  roots,  wash  the 
soil  off,  and  examine  the  growth  of  the  roots.  How  wide  an  area 
do  they  occupy  in  the  ground  ?  How  near  the  surface  do  they 
lie  at  4  inches'  distance  from  the  hill  1  How  near  the  surface  are 
they  at  distances  of  6  inches  and  1 2  inches  from  the  hill  ? 

Once  each  week  for  the  first  six  or  eight  weeks  after  planting, 
try  to  examine  the  roots  of  a  hill  of  corn  and  take  measurements 
of  the  spread  and  depth  they  have  made,  and  their  nearness  to  the 
surface  at  4,  6,  and  12  inches  from  the  hill.  This  experiment  re- 
quires considerable  manual  labor  and  patience  to  carry  it  through 
so  that  it  shall  have  value.  Each  week  it  will  be  necessary  to  dig 
a  deeper  trench  about  the  hill  of  corn  and  use  more  care  to  remove 
the  soil  without  injuring  the  roots.  However,  it  is  of  great  im- 
portance to  the  corn  growers  to  know  how  the  roots  of  the  corn 
plant  develop  and  just  how  they  lie  beneath  the  surface. 

To  test  the  effects  of  deep  cultivation,  in  which  the  roots  of  the 
corn  plant  are  cut  oflf,  a  simple  tool  can  be  made  by  fastening  a 


70  MANUAL  OF  AGRICULTURE 

handle  to  a  solid  block  of  wood  about  6  inches  square  and  2  inches 
thick ;  then  get  a  blacksmith  to  make  a  thin  steel  blade  with 
three  holes,  so  that  it  can  be  screwed  to  the  block  in  such  a  way 
that  it  will  project  below  two,  four,  or  six  inches,  as  desired.  With 
this  implement  it  is  possible  to  run  along  the  side  of  a  row  and 
prune  the  corn  roots  at  any  one  of  these  three  depths.  A  strip  of 
lath  fastened  to  the  top  of  the  block  and  extending  to  one  side  will 
keep  the  knife  at  the  desired  distance  from  the  hill. 

This  pruning  of  the  roots  may  also  be  done  with  a  spade  by 
tightly  bolting  two  strips  of  wood  on  each  side  of  the  blade  to  serve 
as  guards,  and  control  the  depth  to  which  it  can  be  thrust  into  the 
ground.  By  loosening  the  bolt  at  the  ends  of  the  strips,  the  guards 
may  be  raised  or  lowered. 

Select  a  plot  where  the  corn  is  of  uniform  growth.  Lay  off  8 
rows,  each  containing  25  hills,  and  treat  each  row  according  to  the 
following  directions  :  — 

Row  L    Shallow  cultivation  with  a  garden  rake. 

Row  2.    Roots  pruned  4  inches  from  hill  and  2  inches  deep. 

Row  3.    Roots  pruned  4  inches  from  hill  and  4  inches  deep. 

Row  4.    Roots  pruned  4  inches  from  hill  and  6  inches  deep. 

Row  5.    Roots  pruned  8  inches  from  hill  and  4  inches  deep. 

Row  6.    Roots  pruned  8  inches  from  hill  and  6  inches  deep. 

Row  7.    Shallow  cultivation  with  garden  rake. 

The  cultivation  and  pruning  should  be  the  same  on  all  four  sides 
of  each  hill. 

The  pruning  should  be  done  whenever  the  corn  is  cultivated, 
for  the  purpose  of  the  experiment  is  to  compare  the  results  from 
deep  and  shallow  cultivation  in  ordinary  farm  practice. 

After  each  pruning  of  the  roots,  observe  whether  any  of  the 
rows  wilt  or  show  injury. 

Take  measurements  of  the  growth  in  height  of  different  rows. 
At  husking  time,  harvest  and  weijrh  the  corn  from  each  row  sepa- 


STUDIES  ABOUT  CROPS  71 

rately  and  record  the  results.     Make  a  written  statement  of  the 
conclusions  reached  by  this  experiment. 


Exercise  31 
Corn  Breeding :  Selection  of  Seed 

The  purpose  of  this  exercise  is  to  impress  upon  the  minds  of  the 
students  the  fact  that  individual  characters  of  plants  are  trans- 
mitted from  parent  to  offspring,  as  in  the  case  of  animals ;  and 
therefore,  by  selection  of  seed,  the  plant  breeder  may  exercise  large 
control  in  securing  desired  qualities  in  the  crops  that  he  raises. 

Get  permission  from  some  farmer  for  the  class  in  agriculture  to 
go  through  his  corn  field  in  the  early  part  of  September  and  mark 
certain  plants  that  show  striking  individual  characters.  For  in- 
stance, find  a  corn  plant  that  bears  its  ear  very  high  on  the  stalk, 
and  another  plant  equally  vigorous  that  carries  its  ear  lower  than 
the  average  plants.     Record  the  height  of  each  ear. 

Mark  two  other  plants,  one  of  which  has  two  good  ears,  while 
the  second  has  but  one.  Again,  select  a  corn  plant  that  is  firmly 
rooted  and  stands  erect ;  and  in  contrast,  a  plant  that  is  weak  in 
its  root  and  has  fallen  down.  Also  find  a  plant  that  shows  a 
strong  tendency  to  "  sucker,"  and  another  free  from  suckers. 

When  the  com  is  fully  mature,  secure  from  the  farmer  the  ears 
on  the  plants  that  you  have  marked,  carefully  number  or  label 
them,  and  record  the  special  characteristic  for  which  the  plant  was 
selected.  Also  select  two  ears  from  the  crib  of  the  same  variety 
which  have  kern&s  of  distinctly  different  types,  one  square  in 
shape  and  the  other  rounded. 

This  will  give  ten  ears  for  the  experiment.  Now,  if  possible, 
lay  off"  a  plot  2  rods  X  5  rods,  which  will  permit  of  10  rows,  each 


Row 

1. 

Character 

Row 

2. 

Character 

Row 

3. 

Character 

Row 

4. 

Character 

Row 

5. 

Character 

Row 

6. 

Character 

Row 

7. 

Character 

Row 

8. 

Character 

Row 

9. 

Character 

Row 

10. 

Character 

72  MANUAL  OF  AGRICULTURE 

having  25  hills.     Plant  each  row  from  the  seed  of  a  single  ear  as 
follows :  — 

high  ear. 
low  ear. 

two  ears  to  a  stalk, 
single  ear  to  a  stalk, 
strong,  erect  stalk, 
weak,  prostrate  stalk, 
tendency  to  produce  suckers, 
free  from  suckers, 
square-shaped  kernels, 
round-shaped  kernels. 
Give  the  same  treatment  to  all  the  rows;  observe  during  the 
season  whether  the  plants  of  any  of  the  rows  show  peculiarities  of 
growth  corresponding  *to  the  parent  plant,  and  make  a  record  of 
what  you  observe. 

At  the  end  of  the  season  tabulate  the  results  of  the  experiment 
as  follows  :  — 

Row  1.    Average  height  of  ears. 
Row  2.    Average  height  of  ears. 

Difference  between  the  average  heights  of  the  high  and  the  low 
ears. 

Compare  the  average  height  of  the  high  ears  with  height  of  the 
seed  ear. 

Compare  the  average  height  of  the  low  ears  with  the  height  of 
the  seed  ear. 

Row  3.  What  per  cent  of  the  plants  have  more  than  one  ear? 
Row  4.  What  per  cent  of  the  plants  have  more  than  one  ear  ? 
Row  5.  What  per  cent  of  the  plants  stand  erect  ? 
Row  6.  What  per  cent  of  the  plants  stand  erect  ? 
Row  7.  What  per  cent  of  the  plants  have  suckers? 
Row  8.  What  per  cent  of  the  plants  have  suckers  ? 


STUDIES  ABOUT  CROPS  73 

Row    9.  What  per  cent  of  the  ears  have  square  kernels  ? 
Row  10.  What  per  cent  of  the  ears  have  round  kernels? 


Exercise  32 

Corn  Breeding  :   Practice  in  Detasseling 

Prepare  a  plot  of  ground  (2  rods  wide  and  of  any  length)  for 
an  experiment  in  com  breeding.  This  width  of  plot  will  allow  for 
10  rows,  and  the  hills  should  be  3^  feet  apart  in  the  row. 

Use  as  seed  the  best  ten  ears  of  corn  that  you  can  get.  Num- 
ber the  ears  and  the  rows,  and  plant  each  row  with  seed  from  the 
ear  of  corresponding  number.  As  soon  as  the  tassels  begin  to  ap- 
pear, they  should  be  removed  from  all  the  plants  in  eveiy  alternate 
row. 

The  work  of  detasseling  is  performed  in  this  way :  The  tassels 
should  not  be  cut  off,  as  that  is  likely  to  injure  the  plant ;  but  as 
soon  as  the  tassel  is  sufficiently  developed,  and  before  the  pollen  is 
matured,  a  careful  pull  will  separate  it  from  the  stalk  at  the  top 
joint.  It  will  be  necessary  to  go  over  the  plot  several  times  to 
make  sure  that  every  tassel  is  removed  from  these  rows  before  they 
ripen  their  pollen,  for  the  tassels  will  not  appear  on  every  plant  at 
the  same  time. 

From  the  rows  that  are  not  detasseled  remove  all  undesirable 
plants,  i.e.  (a)  those  that  produce  no  ears ;  (6)  those  that  show  a 
tendency  to  grow  suckers  ;  (c)  those  that  are  weak  in  their  roots  ; 
and  (d)  those  that  show  any  smut. 

Seed  ears  are  to  be  selected  only  from  the  detasseled  rows,  be- 
cause with  these  plants  there  is  absolute  certainty  that  every  ker- 
nel has  been  produced  by  cross-pollination. 

This  exercise  is  given  mainly  to  furnish  practice  in  the  method 
that  is  generally  followed  now  by  breeders  of  pedigreed  seed  corn. 


74  MANUAL   OF  AGRICULTURE 

Harvest  and  weigh  the  corn  from  each  row  separately,  and  keep 
a  record  of  results.  If  it  is  possible  to  continue  this  experiment 
from  year  to  year,  select  the  seed  to  be  used  the  following  year 
from  the  highest-yielding  rows  that  were  detasseled.  Observe 
whether  detasseling  seems  to  increase  or  decrease  the  yield  as  com- 
pared with  the  rows  bearing  tassels. 


Exercise  33 

Experiment  in  Hand  Pollination 

In  order  to  be  certain  in  regard  to  both  sire  and  dam  in  the 
production  of  seed,  it  is  necessary  to  protect  the  pistils  of  the  plants 
that  are  to  bear  the  seed  from  any  possible  contact  with  the  pol- 
len grains  of  their  own  stamens  or  of  those  of  ,any  other  plants 
except  the  ones  chosen  for  the  sires. 

To  do  this  in  the  case  of  corn,  make  a  number  of  little  bags  of 
cotton  cloth  about  6  inches  wide  and  10  inches  long.  Narrow 
strips  of  the  same  cloth  stitched  in  the  middle  to  the  edge  of  the 
mouth  of  the  sack  make  convenient  strings  for  holding  the  bags 
in  place. 

Before  any  of  the  silk  appears  on  the  tips  of  the  young  ears 
that  have  been  selected  for  the  dams,  draw  over  each  of  the  ears^ 
one  of  the  cloth  bags  and  tie  it  securely  about  the  shank  of  the 
ear. 

For  mating  with  each  dam,  select  the  same  number  of  corn  plants 
to  serve  as  sires,  and  as  soon  as  the  pollen  on  the  tassels  of  these 
plants  becomes  mature  and  begins  to  shed,  shake  it  off  carefully 
from  one  of  the  plants  into  an  open  dish ;  now  remove  the  sack 
from  the  ear  of  one  of  the  dams  and  rub  the  ends  of  the  silks  care- 
fully in  the  pollen  that  has  been  collected  in  the  bottom  of  the 
dish,  making  sure  that  every  one  of  the  silks  comes  in  contact  with 


STUDIES  ABOUT  CROPS  75 

a  grain  of  the  pollen.  Then  replace  the  sack  over  the  end  of  the 
ear,  and  do  not  remove  it  again  until  two  or  three  weeks  later. 

To  determine  the  difference  in  the  vigor  of  seed  produced  by 
cross-pollination  from  that  resulting  from  self-pollination  (pistils 
fertilized  by  the  pollen  of  the  same  plant),  pollinate  the  silks  of 
three  or  four  ears  with  pollen  taken  from  the  tassels  of  the  same 
plants.  Mark  the  ears  thus  produced,  and  the  following  year  plant 
a  few  rows  with  seed  from  these  ears  by  the  side  of  rows  where 
cross-pollinated  seed  was  used,  and  compare  results. 

Cross-pollinate  the  silk  of  an  ear  of  white  corn  with  the  pollen 
from  the  tassel  of  yellow  corn',  and  vice  versa.  What  is  the  color 
of  the  cob  grown  on  the  stalk  of  white  corn  ?  What  is  the  color 
of  the  grain  on  this  ear  ?  What  is  the  color  of  the  cob  on  the  stalk 
of  yellow  corn  ?     What  is  the  color  of  the  grain  ? 

On  one  ear  do  not  remove. the  sack  nor  apply  pollen  to  the  silk. 
After  several  weeks  take  off  the  sack,  and  notice  how  long  the  silk 
has  grown.     What  does  this  teach? 

XXVIII.  —  Observation  Studies  in  the  Cornfield 

The  development  of  the  present  breeds  of  cattle  and 
other  live  stock  plainly  shows  how  careful,  systematic, 
and  intelligent  selection  has  improved  the  animals. 
Plants  respond  to  breeding  and  selection  as  readily  as 
do  animals,  and  there  is  no  longer  any  doubt  that  va- 
rieties of  corn  may  be  further  improved  by  similar 
methods.  Experiments  conducted  by  the  Illinois  Ag- 
ricultural Experiment  Station  and  other  similar  insti- 
tutions have  conclusively  shown  that  the  composition 
of  the  corn  kernel  may  be  varied  at  the  will  of  the  careful 
breeder  ;  that  it  is  possible  to  increase  or  decrease  the 


76  MANUAL   OF  AGRICULTURE 

amount  of  oil,  or  of  starch,  or  of  protein  by  selection  of 
seed. 

It  is  equally  true  that  greater  variations  may  be 
made  in  the  ears  or  the  stalks  by  selection.  The 
amount  of  husks,  length  of  shank,  size,  and  height  of 
stalk,  position  of  ear  on  the  stalk,  the  number  of  leaves, 
and  in  fact  every  physical  characteristic,  can  be  varied 
in  a  short  time  by  simple  selection.  It  is  just  as  im- 
portant to  know  the  character  of  every  part  of  the  corn 
plant  as  to  know  every  characteristic  of  the  animal. 
The  size,  shape,  and  characteristic  of  the  stalk  strongly 
influence  the  development  of  the  ear  and  kernel  of  corn. 

Get  permission  from  a  farmer  whose  land  is  conven- 
ient to  the  school  to  use  his  cornfield  for  the  purpose  of 
making  a  study  of  the  corn  crop.  Have  each  pupil 
work  on  separate  plots,  ten  hills  square,  and  make  his 
notes  and  records  with  reference  to  the  following 
points :  — 

Exercise  34 

Field   Work  with  Corn 

Name  of  variety Size  of  field 

1.  Date  the  corn  matures  :  (a)  roasting  ear 

(6)  dented  or  glazed (c)  ripe 

2.  Height  of  corn  ;  average  of  ten  plants feet 

inches 

3.  Total  number  of  leaves  on  ten  plants,  taken  from  different  hills 
Average  number  of  leaves  per  plant 

4-  Total  number  of  leaves  below  the  ear  on  ten  plants,  taken  from 
different  hills Average 


STUDIES  ABOUT  CROPS  .  77 

5.    Figure  the  total  leaf  surface  on  five  average  corn  plants  (for  each 
leaf  blade  take  twice  the  product  of  the  length  and  average  width) 


6.  Length  of  ear  stem,  or  shank  (distance  from  joint,  or  node,  to 
base  of  ear) .     Average  of  ten  plants 

7.  The  ear  stem,  or  shank,  may  be  (1)  large,  —  nearly  or  quite 
the  diameter  of  the  cob  ;  (2)  medium,  — or  about  half  the  diameter  of 
the  cob  ;  (3)  small,  —  or  one  third  or  less  the  diameter  of  the  cob. 

8.  Husks:  abundant,  medium,  scarce 

9.  Husks:  close,  medium,  loose 

10.  Measure  ten  hills  square  ;  give  number  of  ears  on  these  one 
hundred  hills Average  per  hill ■ 

11.  Give  number  of  stalks  in  the  above  area  having  two  or  more 
ears 

12.  Give  number  of  stalks  in  above  area  without  ears  (barren 
stalks)  

13.  Give  average  height  of  ears  in  above  area 

14.  Position  of  the  ears  on  stalks :  pointing  upward  ;  horizontal ; 
pointing  downward 

15.  Distance  apart  of  hills  each  way 

16.  Give  number  of  hills  per  acre 

17.  Measure  off  one  acre  which  represents  a  good  average  of  the 
field ;  husk  one  twentieth  of  this,  and  after  weighing  same  carefully, 
estimate  the  average  yield  of  field 

18.  If  hills  of  corn  are  3  feet  6  inches  each  way,  how  many  hills 
to  the  acre  ? 

19.  If,  in  a  field  of  corn  planted  3  feet  6  inches  each  way,  there  is 
on  the  average  1|  pounds  of  corn  to  each  hill,  counting  80  pounds  to 
the  bushel  to  allow  for  shrinkage,  what  is  the  yield  per  acre  ? 

20.  If  corn  is  planted  3  feet  6  inches  each  way,  and  when  mature 
is  cut  and  put  into  shocks,  each  shock  containing  the  corn  from  an  area 
14  hills  square,  how  many  shocks  to  the  acre  ? 

How  many  of  the  shocks  are  16  hills  square  ? 


78 


MANUAL  OF  AGRICULTURE 


The  following  table  will  assist  in  making  accurate  estimate  of 
the  amount  of  land  in  different  fields  or  plots  :  — 

10  rods  X  16  rods  =  1  acre. 

8  rods  X  20  rods  =  1  acre. 

5  rods  X  32  rods  =  1  acre. 

4  rods  X  40  rods  =  1  acre. 

5  yards  x  968  yards  =  1  acre. 
10  yards  x  484  yards  =  1  acre. 
20  yards  x  242  yards  =  1  acre, 
40  yards  x  121  yards  =  1  acre. 
80  yards  x    60^  yards  =  1  acre. 


220  feet  x  198 
440  feet  x  99 
110  feet  X  396 
60  feet  X  726 
120  feet  X  363 


feet  =  1  acre. 
feet  =  1  acre. 
feet  =  1  acre, 
feet  =  1  acre, 
feet  =  1  acre. 


240  feet  x  181.5  feet  =  1  acre. 
200  feet  x  108.9  feet  =  ^  acre. 
100  feet  X  145.2  feet  =  i  acre. 
100  feet  X  108.9  feet  =  i  acre. 


Area  of  One  Acre 

10  square  chains  =  1  acre. 

160  square  rods     =  1  acre. 

4,840  square  yards   =  1  acre. 

43,560  square  feet      =  1  acre. 

640  acres  =  1  square  mile. 
36  square  miles  (six  miles  square)  =  1  township. 


Exercise  35 

Studies  of  an  Ear  of  Corn 

In  order  to  become  accustomed  to  the  essential  points  in  study- 
ing the  characteristics  of  corn,  the  following  suggestions  are  ap- 
pended. Take  ten  ears  each  of  two  or  more  different  varieties, 
preferably  one  yellow,  one  white,  selecting  ears  as  uniform  and 
true  to  the  variety  type  as  possible.  To  get  a  close  comparative 
study,  it  is  advisable  to  lay  all  the  samples  on  a  table  side  by  side. 
After  studying  the  characteristics  carefully,  use  this  list  for  refer- 
ence and  bring  out  by  example  the  points  mentioned ;  then  the 
work  of  scoring  the  samples  may  be  taken  up,  following  carefully 
the  several  points  indicated  on  the  corn  score  card  as  given  on 


STUDIES  ABOUT  CROPS  79 

page  84  of  this  manual,  and  noting  carefully  the  explanatory  notes. 
Each  sample  of  ten  ears  should  be  marked  and  known  as  "  Ex- 
hibit A,"  "  Exhibit  B,"  etc.  The  letters  (a)  and  (b),  as  used  below, 
refer  to  the  sample  under  examination,  and  it  is  intended  that  the 
corresponding  characteristics  possessed  by  each  variety  be  marked 
in  the  blank  space. 

Name  of  variety  (a) (h) 


I.  Color  of  grain:  white;  yellow;  golden.    («) '. (&) 

II.  Color  of  cob:  white  ;  light  red  ;  dark  red.   (a) (6) 

III.  Surface  of  ear  :  smooth;  rough;  very  rough,    (a) 

(6) 

IV.  Rows  of  kernels :  — 

1.  Are  rows  in  distinct  pairs  (alternate  spaces  between  rows  of 
kernels  wider  than  the  others)  ?     (a) (6) 

2.  Number  of  rows  (count  three  inches  from  butt),    (a) 

(&) 

3.  Number  of  rows  lost  (disappearing  after  extending  three  inches 
or  more  from  butt),    (a) (6) , 

4.  Spaces  between  rows:  medium;  narrow;  wide,     (a) 

(&) 

5.  Are  rows  straight  (parallel  with  cob)  ?  (a) (6) 


6.   Are  rows  turned  to  the  right  or  left  (twisted  to  right  or  left 
of  a  straight  line  from  butt  to  tip)  ?    (a) (&) 

V.  Grains  on  cob  :   dovetailed  or  mosaic-like  ;  firm  ;   loose ;  very 
loose  :     (rt) (&) 

VI.  Shape  of  ears  :  — 

1.   Cylindrical  (uniform  in  circumference  from  butt  to  tip),     (a) 
(6) 


80  MANUAL  OF  AGRICULTURE 

2.  Partly  cylindrical  (uniform  in  circumference  for  a  portion  of 
length,     (a) (6) 

3.  Slightly  tapering  (taper  slight  and  regular),    (a) 

(6) 

4.  Distinctly  tapering  (taper  very  apparent),     (a) . 

(6) 

5.  Very  tapering  (extremely  tapering),     (a) (6) 

6.  Are  the  ears  in  the  exhibit  too  short  or  too  long  for  their  cir- 
cumference ?  (The  proper  proportion  is  for  northern  Illinois,  6.75- 
7.50  inches  in  circumference  to  9-10  inches  in  length  ;  for  central  and 
southern  Illinois,  7-7.75  inches  in  circumference  to  10-11  inches  hi 
length),     (a) (&) 

VII.    Butts  of  ears  :  — 

1.  Even   (entire  end  of  cob  exposed,  with  butt  kernels  at  right 

angles  to  axis  of  cob),     (a) (6) 

2.  Shallow  rounded  (cavity  at   butt   shallow,  broad),    (a) . 

(&) 

3.  Moderately  rounded  (cavity  moderately  deep,  medium  diam- 
eter),    (a) (a) 

4.  Well  rounded  (cavity  at  butt  deep,  small  diameter  where 
the  shank  is  removed,  rows  of  grains  extending  in  regular  order  over 
the  butt),     (a) (6) 

5.  Compressed  (cob  rounded  at  end ;  kernels  at  butt  flat,  smooth 
and  short,  indicating  a  tight  husk),    (a) ■■ — (&) 

6.  Enlarged  (large  butt  with  no  extra  rows  of  kernels), 
(a) (&) 

7.  Expanded  (large  butt  caused  by  extra  rows  of  kernels). 

(«) (&) 


STUDIES  ABOUT  CROPS  81 

VIII.  Tips  of  ears  :  — 

1.  Kernels  in  rows  (rows  may  be  traced  to  tip),     (a) 

(6) 

2.  Flat  (cob  flattened  at  tip),     (a) (6) . 

3.  Filled  (entire  end  of  cob  covered  with  kernels) .    (a) 

(&) 

4.  Capped  (a  central  kernel  projecting  from  filled  tip) .  (a) 

(&) 

IX.  Kernels :  — 

1.   Firm  (rigid  on  cob),     (a) (h) 


2.   Loose  (movable  on  cob),    (a) (6). 


3.  Upright  (at  right  angles  with  surface  of  cob),   (a)- 
(6) 

4.  Sloping  (leaning  toward  tip.)     (a) (6). 


6.   Square  at  top  (comers  not  rounded  at  summit),     (a) 

(6) 

6.  Shoe-peg  form  (long,  narrow  kernel  holding  size  to  tip) . 

(a) ^(&) 

7.  Rounded  corners    (corners    rounded    at    summit    and    base). 

(«) (&) 

8.  Beaked  (with  long,  sharp,  tapering  projection),     (a) 

(6) 

X.   Junction  of  ear  stem,  or  shank,  with  ear :    large ;    medium ; 
small,     (a) (&) 

XL   Average  length  of  ears  :  (a) (b) 


XII.     Average  circumference  of  ears  one-third  distance  from  butt; 
(a) —(b) 


82  MANUAL  OF  AGRICULTURE 

XIII.  Give  ratio  of  circumference  of  average  ear  to  length  of  aver- 
age ear  (divide  length  of  ear  by  circumference  of  ear).  [The  proper 
proportion  of  circumference  to  length  is  as  3  to  4 ;  or  for  medium 
varieties  7.5  to  10  inches.]     (a) (6) 

XIV.  Weigh  five  ears  from  each  sample,  taking  each  alternate  ear  j 
give  average  weight  of  ears,     (a) (h) 

XV.  Shell  these  five  ears  and  give  average  weight  of  cobs, 
(a) (&) 

XVI.  Give  average  circumference  of  cobs  one-third  distance  from 
butt,     (a) (6) 

XVII.  Give  ratio  of  circumference  of  average  cob  to  average  ear 

(divide  circumference  of  ear  by  circumference  of  cob) .     (a) 

(6) 

XVIII.  Give  percentage  of  grain :  [Note. —  To  determine  the  per- 
centage or  proportion  of  grain  to  cob,  select  every  alternate  ear  in  the 
exhibit  and  weigh  same.  Shell  and  weigh  the  cobs ;  subtract  the 
weight  of  the  cobs  from  the  total  weight  of  the  ears,  giving  weight  of 
shelled  corn.  Divide  the  weight  of  shelled  corn  by  the  total  weight  of 
ears,  which  will  give  the  per  cent  of  grain.  The  per  cent  of  grain 
should  be  from  86  to  90.  ]     (a) (5) 

XIX.  Count  the  number  of  kernels  of  corn  on  the  largest  ear  and 
on  the  smallest  ear  in  each  exhibit,     (a) (6) 

XXIX.  —  Judging  and  Scoring  Corn 

The  object  of  corn  judging,  like  that  of  stock  judg- 
ing, is  to  fix  more  clearly  in  the  mind  certain  ideals  of 
excellence  which  shall  serve  as  standards  of  comparison 
to  aid  in  the  improvement  of  the  products  we  are  work- 
ing to  secure. 


STUDIES  ABOUT  CROPS  83 

It  is  to  the  interest  of  the  corn  grower  to  produce  the 
largest  yields  and  the  best  quality  of  this  grain  at  the 
greatest  profit. 

The  careful  study  of  corn  has  taught  that  certain 
characters  of  ear  and  kernel  are  closely  associated  with 
large  yields  and  high  quality.  Taking  these  as  the 
basis  for  a  standard  of  perfection,  the  Illinois  Corn 
Growers'  Association  has  formulated  a  score  card  on 
which  are  indicated  the  several  points  to  be  considered 
in  estimating  the  merits  of  a  sample  of  corn  and  the 
relative  degrees  of  importance  of  these  points. 

It  has  been  found  that  the  use  of  such  a  score  card  is 
a  valuable  aid  to  the  judge  or  students  in  comparing 
and  determining  the  relative  merits  of  several  samples 
of  corn. 

CORN   SCORE   CARD 
Name  of  Scorer Date . 


Post  Office Exhibit  No.. 

Standard  Measueements  of  Variety 

Name  of  Variety 

Length 

Circumference 


Proportion  of  Grain  to  Cob. 


The  Corn  Score  Card 

The  following  is  the  score  card  of  the  Illinois  Corn  Growers' 
Association,  as  revised  and  adopted  by  that  Association  January 
29,  1908,  This  should  be  used  in  judging  varieties  or  samples 
not  named,  and  also  where  the  exhibit  is  not  made  under  a  variety 
classification. 


84 


MANUAL  OF  AGRICULTURE 


Measurements  for  General  Score  Card 


Northern  Illinois      .     .     .     . 
Central  and  southern  Illinois 


Length. 
Inches. 


9-10 
10-11 


ClECUMFER- 

ENCE. 

Inches. 


6.75-7.50 
7.00-7.76 


Peoportion 
OF  Corn 
TO  Cob. 


88  per  cent 
88  per  cent 


Points. 


1.  Uniformity  of  exhibit     .     .     .     . 

2.  Shape  of  ear 

3.  Length  of  ear 

4.  Circumference  of  ear     .... 

5.  Tips  of  ear 

6.  Butts  of  ear 

7.  Kernel  uniformity 

8.  Kernel  shape 

9.  Color  in  grain  and  cob  .... 

10.  Space  between  rows      .... 

11.  Space  between  kernels  at  cob 

12.  Vitality  or  seed  condition  .     .     . 

13.  Trueness  to  type 

14.  Proportion  of  shelled  corn  to  cob 

Total 


Perfect 
Score. 


5 
10 
10 
5 
5 
5 
5 
5 

10 
5 
5 
10 
10 
10 

100 


Score   of 
Sample. 


Explanation  of  Points 

1.  Uniformity  of  exhibit  :   uniform  in  shape,  length,  and  circumfer- 
ence. 

2.  Shape    of    ears  :  ears  cylindrical,  with  straight    rows    and  with 
proper  proportion  of  length  and  circumference. 

3.  Length  of  ears  :  varies  with  variety  measure. 

4.  Circumference  of  ears  :  varies  with  the  variety  measure. 


STUDIES  ABOUT  CROPS  85 

5.  iTips  of  ears:  oval  shape  and  regularly  filled  out  with  large, 
dented  kernels. 

6.  Butts  of  ears  :  kernels  rounded  over  the  end  of  the  cob  in  regular 
manner,  leaving  a  deep  depression  when  shank  is  removed. 

7.  Kernel  uniformity  :  kernels  from  the  same  ear  and  from  the  sev- 
eral ears  uniform  in  size  and  shape. 

8.  Kernel  shape  :  kernels  deep,  wedge-shaped,  full  at  germ  end. 

9.  Color  :  free  from  mixture  and  true  to  variety  color. 

10.  Space  between  rows  :  furrow  between  rows  and  space  caused  by 
round  corners  of  kernels,  which  should  be  narrow,  deep,  and  sufficient  for 
perfect  ventilation. 

11.  Space  between  kernels  at  cob :  space  in  row  between  kernels  at 
cob. 

12.  Vitality  or  seed  condition:  ripe,  sound,  dry,  and  of  strong  vitality. 
Grains  of  a  pinkish  color  objectionable.  Three  dead  ears  shall  disqualify 
an  entire  exhibit. 

13.  Trueness  to  type :  conforming  to  variety  characteristics  in  variety 
classes,  and  to  the  prevailing  type  in  general  classes. 

14.  Proportion  shelled  corn  to  ear. 

Explanatory  :  How  to  study  and  apply  the  Points  of  the 

Score  Card 

Note  A. —  In  all  exhibits  made  prior  to  November  15  of  each  year, 
all  standards  of  length  and  circumference  shall  be  increased  one-half 
inch,  and  standards  of  per  cent  shall  be  reduced  two. 

Note  B.  —  The  length  and  circumference  of  the  general  score  card, 
for  the  northern  district,  shall  be  used  in  judging  the  standard  varie- 
ties, when  shown  within  that  district  of  the  state. 

Note  C.  —  Exhibitors  may  remove  two  kernels  side  by  side  from  the 
same  row  at  the  middle  of  the  ear  for  kernel  examination. 

1.  The  deficiency  and  excess  in  length  of  all  ears  shall  be  added 
together,  and  for  every  inch  thus  obtained,  a  cut  of  one  point  shall  be 
made.  Should  the  deficiency  in  length  exceed  ten  inches,  a  cut  of 
two  points  for  each  additional  inch  shall  be  made  on  the  total  score. 
In  determining  length,  measure  from  the  extreme  tip  to  the  extreme 
butt. 

1  It  is  recommended  that  judges  interpret  this  rule  very  liberally, 
and  that  tips  be  not  heavily  cut  for  slight  deficiency,  so  far  as  being 
filled  over  with  kernel  is  concerned. 


86 


MANUAL  OF  AGRICULTURE 


2.  The  deficiency  and  excess  in  circumference  of  all  ears  not  con- 
forming to  the  standard  of  the  variety  shall  be  added  together,  and 
for  every  inch  thus  obtained,  a  cut  of  one  point  shall  be  made.  Meas- 
ure the  circumference  at  about  one-third  the  distance  from  the  butt  to 
the  tip  of  the  ear. 

3.  In  determining  the  proportion  of  corn  to  cob,  weigh  each  alter- 
nate ear  in  the  exhibit.  Shell  and  weigh  the  cobs,  and  subtract  from 
weight  of  ears,  giving  weight  of  corn.  Divide  the  weight  of  corn  by 
the  total  weight  of  ears,  to  get  the  per  cent  of  corn.  For  each  per  cent 
short  of  the  standard  for  the  variety,  a  one-point  cut  shall  be  made. 

4.  In  judging  color,  a  red  cob  in  white  corn  or  a  white  cob  in  yellow 
corn  shall  be  cut  ten  points.  Eor  one  mixed  kernel,  a  cut  of  one-fifth 
of  a  point  shall  be  made  ;  for  two,  two-fifths  of  a  point ;  for  three,  three- 
fifths  of  a  point ;  for  four,  four-fifths  of  a  point ;  for  five  or  more,  a 
one-point  cut  shaU  be  made.  Kernels  missing  from  the  ear  shall  be 
counted  as  mixed,  at  the  discretion  of  the  judge.  Difference  in  shade 
of  color  of  grain  or  cob  shall  be  scored  according  to  variety  character- 
istics. 

Measurements  for  Named  Varieties 

Certain  varieties  of  com  have  been  grown  and  bred  for  a  long  time 
by  men  who  by  improved  methods  have  developed  certain  character- 
istics of  stalk  and  ear,  such  as  color  and  shape  of  kernel,  shape  and 
size  of  ear,  maturity,  etc.  Furthermore,  each  variety  has  its  peculiar 
length,  circumference,  and  proportion  of  com  to  cob.  Based  on  a 
careful  study  of  the  best  samples  of  the  different  varieties  recognized 
by  the  Illinois  Com  Growers'  Association,  these  variety  standards  are 
as  follows :  — 


Keid's  Yellow  Dent  . 
Leaming  .... 
Boone  County  White 
Kiley's  Favorite  .  . 
Golden  Eagle  .  .  . 
Silver  Mine .... 
Champion  White  Pearl 


Length. 


10  to  11  in. 
10  to  11  in. 
10  to  11  in. 

9  to  10  in. 

9  to  10  in. 

9  to  10  in. 

8  to  9  in. 


Circumference. 


7  to  7.75  in. 
7  to  7.75  in. 
7  to  7.75  in. 
6.75  to  7.5  in. 
7  to  7.75  in. 
6.75  to  7.5  in. 
6.75  to  7.5  in. 


Pee  Cent  of 
Corn  to  Cob. 


88 
88 
88 
90 
90 
90 
85 


STUDIES  ABOUT  CROPS  87 

Suggestions  for  preparing  Exhibit 

In  judging  corn,  ten  ears  usually  constitute  an  exhibit  sample.  It  is 
desirable  that  samples  be  laid  out  side  by  side  on  a  table  where  a  good 
light  may  be  had. 

There  is  no  better  way  to  sort  and  select  seed  corn  or  to  prepare  a 
sample  for  exhibition  than  to  place  the  ears  from  a  bushel  or  so  of 
selected  corn  upon  a  board  or  table,  with  the  tips  all  pointing  one  way. 
Select  the  most  perfect  ear  you  can  find,  something  which  is  your  ideal 
type.  Then,  with  this  ear  in  your  left  hand,  go  over  all  the  ears  of 
corn  upon  the  table,  discarding  those  showing  too  great  a  variation 
from  type  in  size,  length,  shape,  roughness,  and  the  size,  shape,  and 
indentation  of  kernel,  etc. 

.  In  preparing  corn  for  exhibition,  the  ears  should  be  groomed  so  as 
to  present  the  best  possible  appearance  by  removing  all  husk,  silks,  and 
shanks,  but  do  not  mutilate  or  cut  the  ear  itself  in  any  way.  Neither 
is  it  allowable  to  remove  mixed  kernels  and  substitute  kernels  of  a 
proper  color.  The  ears  should  be  handled  carefully,  that  no  kernels  be 
knocked  off,  for  kernels  that  are  missing  are  usually  regarded  as  mixed, 
and  the  usual  cut  made  for  such  imperfection.  If  the  exhibit  is  to  be 
sent  away,  each  ear  should  be  carefully  wrapped  in  a  piece  of  newspa- 
per or  other  protection  and  firmly  packed  in  a  box. 

Note  A.  —  The  score  card  cannot  be  used  in  absolutely  mathemati- 
cal sense.  No  set  rules  can  be  given  ;  it  is  largely  a  matter  of  the 
exercise  of  good  sound  judgment  and  patient  practice  on  the  part  of 
the  scorer.  Where  the  number  of  points  to  be  cut  is  not  fixed  by 
rules  for  judging,  such  as  circumference,  length,  etc.,  the  cut  made 
should  be  in  accordance  to  the  degree  of  variance  of  each  ear  from 
value  of  the  perfect  ear,  as  fixed  by  standard. 

Remarks 

As  has  been  said  before,  the  score  card  is  intended  to  be  largely 
suggestive.  It  is  not  an  infallible  guide,  but  is  to  be  used  rather  as  a 
staff,  or  cane,  as  it  were,  to  help  us  and  to  give  a  little  more  intelli- 
gent  direction  as  to  the  essential  points  to  be  observed  in  selecting 
corn  either  for  seed  or  for  exhibition  purposes. 

It  should  be  borne  in  mind  that  while  these  ideal  points  and  char- 
acteristics of  the  score  card  as  described  in  the  foregoing  explanatory 


88  MANUAL   OF  AGRICULTURE 

notes  are  desirable,  other  things  being  equal,  the  lack  of  perfection 
may  not  prevent  a  variety  from  producing  high  yields  or  having  in 
other  particulars  desirable  qualities.  For  example,  the  cob  should  be 
neither  too  large  nor  too  small.  It  is  evident  that  of  two  ears  of  equal 
size  and  compactness,  the  one  with  the  small  cob  will  have  a  deeper 
kernel  and  will  contain  more  grain.  On  the  other  hand,  while  the 
small  cobs  may  show  a  larger  proportion  of  grain,  yet  the  total  weight 
of  the  ears  may  be  much  less  and  the  yield  per  acre  smaller.  A  large- 
sized  cob  is  objectionable  in  that  it  usually  carries  a  larger  per  cent  of 
water,  thus  lowering  the  keeping  quality  of  the  grain  and  its  vitality 
for  seed. 

In  a  well-proportioned  ear  the  shelled  corn  will  occupy  about  the 
same  space  as  did  the  ear  before  it  was  shelled.  It  is  a  good  relation- 
ship where  the  depth  of  grain  is  one  half  the  diameter  of  the  cob,  or 
the  circumference  of  the  ear  twice  that  of  the  cob. 


Exercise  36 
Testing  Corn  for  Seed 

The  purpose  in  testing  seeds  is  to  determine,  before  planting, 
their  vitality  for  germination  and  growth. 

Several  simple  devices  are  used  for  this  work,  the  essential  things 
being  an  arrangement  for  keeping  the  seeds  exposed  to  the  proper 
conditions  of  moisture  and  heat,  and  the  grains  from  each  ear 
separate,  so  that  a  record  of  every  ear  tested  may  be  kept. 

The  following  method  is  recommended  by  the  Agronomy  De- 
partment at  the  University  of  Illinois :  — 

Have  a  tinsmith  make  a  galvanized  tray  1 6  inches  square  and  2 
inches  deep.  Fill  this  tray  with  clean  sawdust,  thoroughly  moistened 
before  being  placed  in  the  tray,  and  pack  it  down  firmly.  If  more 
convenient,  use  sand  in  place  of  sawdust.  Cut  a  piece  of  white 
cotton  cloth  to  fit  inside  the  tray,  and,  with  a  ruler  and  good  in- 
delible pencil,  mark  it  off  into  squares  of  1^  in.  This  will  give 
100  squares,   and    100  ears  of  corn  may  be  tested  at  a  time. 


STUDIES   A^BOtlt  CflOPS         '  89 

"  >' 
Each  square  may  be  numbered,  or  the  first  square  in  each  row. 

Have  a  pane  of  window  glass  of  double  thickness  cut  15 J  inches 

square,  so  that  it  will  fit  rather  loosely  into  the  tray.     The  ears 

to  be  tested  should  be  numbered.     This  may  be  done  by  tying  a 

tag  to  each  ear  or  pinning  it  to  the  butt. 

When  ready  to  fill  the  tester,  take  ear  No.  1  in  the  left  hand, 
and  with  the  blade  of  a  pocketknife  pick  out  a  kernel  two  inches 
from  the  butt.     Lay  this  in  square  No.  1,  germ  side  up. 

Turn  the  ear  one  fourth  round  and  take  a  second  kernel  two  inches 
nearer  the  tip,  placing  this  grain  also  in  the  first  square.  In  the 
same  way,  turning  the  ear  one  quarter  of  its  circumference  and 
moving  two  inches  nearer  the  tip  each  time,  select  kernels  three 
and  four,  the  last  being  taken  two  inches  from  the  tip  end.  Lay 
them  all  in  the  first  square  with  their  germ  sides  up. 

When  the  hundred  squares  are  filled,  each  with  four  kernels, 
from  ears  numbered  to  correspond  with  the  number  of  the  square, 
lay  the  pane  of  glass  carefully  down  on  the  grains  so  as  not  to 
move  them  from  their  places,  and  set  the  tray  where  the  tempera- 
ture will  range  during  the  twenty-four  hours  from  60°  to  80°  F. 
Such  conditions  can  generally  be  found  in  the  family  living  room  or 
near  the  furnace  in  the  cellar. 

If  the  moist  sawdust  or  sand  is  not  packed  into  the  tray  until 
you  are  ready  to  place  the  grains  in  the  tester,  no  more  moisture 
will  be  needed.  As  the  glass  does  not  fit  tightly  in  the  tray,  there 
will  be  sufficient  access  of  air  for  the  seeds. 

Without  removing  the  glass,  it  will  be  easy  to  see  how  the  seeds 
are  germinating.  At  the  end  of  the  sixth  or  seventh  day,  remove 
the  glass  and  discard  all  kernels  that  have  not  put  forth  both  a 
vigorous  rootlet  and  a  shoot  an  inch  or  more  in  length.  No 
ear  should  be  used  for  seed  unless  the  four  kernels  germinate  and 
show  strong  vitality.  A  class  may  work  together  on  this  exercise. 
Keep  the  records  of  all  results. 


V    ^V' 


y- 


JD    *4vJM-  I    f 


p—i1i^*rt jgj^^Hl  II ■■  ii     ^i?.- '.^a.»,,^raa'».i— ja>«»^^ .< ■  i ^  it  ijrtiiirip 


267522 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


•I'  "''^iy-.: .\^^'r 


':nmw'tmm 


>■.f^,;->•Jf^^•■'^■^n■":  ::ip.-.3 


■    ■■    ;'•'*''■  -r^p.'-.' ■'    >•■■:..■  t  ^«     ;-v;m  ■*■■;•.:  ■<V.-''- •,•■-••  ■;      '■ 
:'':r.  ■•■,•,•.■.:  ■M>;^;..V.'.;"V...:.    .'V   ;v.  ."'' •    ;';■>.'■  •.■,i'' /  W^^jr:  :*;■%;::'- ■•< 

,' ,  >•  ■'  -.'■^:  ■.•'■•  ■  ■  ■  ■  v  •'  •  ,  y\-.:,  ''~  >•'.••.-.!»-. .-.h-:-. ■.•:-,•  ^..-.i. 

^'  ..n..   ■■'",•   ■^;.'l  V  •■■■•■.■ ''"^Wv!'fe;icJ^-l<S^^^^ 
^- 1  ■  •'-<  i■'■^■•l•^L: ';■.'■£?■'..•  »S?i!j5?-'lv!; 


